Meaning of competitive exclusion principle. Only one population will thrive; the other population will decrease to zero. If you were to go outside and pick up a handful of dirt, the resulting mass would appear largely uneventful and boring. Competitive exclusion principle: 2 species that use the same resources in the same ways cannot coexist. In ecology, the competitive exclusion principle, sometimes referred to as Gause's law, is a proposition named for Georgy Gause that two species competing for the same limited resource cannot coexist at constant population values. See all Hide authors and affiliations. J    The competitive exclusion principle dictates that two species cannot exist in the same ecological niche. The competitive exclusions principle says that two species cannot exist together if they compete for the same resources. When you boil it all down, we simply harness Mother Nature’s natural response to harmful biology. - Renew or change your cookie consent, /definition/2903/principle-of-competitive-exclusion, WIS Morning Show: Stress Management Do Genders Manage Stress Different, The Safety View: Meet the Author Rob Krete, Safety Talks #22: Being Innovative 2021 - EHS Injury Preventative Tech, WIS Morning Show: Impact of Mental Load and the Unpaid Shift, Safety View: Role of Mental Health in Organizational Performance, Electrolytes: What They Are and Why They Matter for On-the-Job Hydration, Safety Talks #18 - Heat Stress Preparedness, Work Locations and Vocations That Require Hydration Year-Round, Quiz: Test Your Knowledge About Heat and Hydration, 7 Lesser-Known Factors That Contribute to Heat Stress, Safety Benefits of Using Sound Masking in the Office, Protecting Your Hearing on the Job: The 5 Principles of Hearing Protection, Safety Talks #5 - Noise Exposure: Evolving Legislation and Recent Court Actions with Andrew McNeil, What Senior Management Needs to Know About Hearing Protection. One will either die out or migrate, or they will adapt to carve out separate resource niches. This is because, in a competition to survive, they try to consume as many resources as they can, not … In many ways, the soil itself mimics a living organism. We haven’t even mentioned fungi, actinomycetes, microalgae, protozoa, nematodes, and other invertebrates. Gause observed that in such circumstances, population values cannot remain constant. C    Therefore, we decided to take some time to fully explain what competitive exclusion is and how it plays a key role in the majority of our products. competitive exclusion principle [ kəm-pĕt ′ĭ-tĭv ] The principle that when two species compete for the same critical resources within an environment, one of them … N    The principle of competitive exclusion is also known as Gause’s law. The principle of competitive exclusion states that A) two species cannot coexist in the same habitat. This is known as the competitive exclusion principle. The Competitive Exclusion Principle. Fall Arrest Systems: Can You Tie Off at Your Feet? Garrett Hardin . When one species has even the slightest advantage over another, the one with the advantage will dominate in the long term. K    Competitive exclusion is the principle stating that two species competing for the same resources cannot coexist. competitive exclusion principle n. The ecological principle that when two species compete for the same critical resources within an environment, one of them will eventually outcompete and displace the other. If two species attempt to occupy the same niche, one species will be better at competing for limited resources and will eventually exclude the other species. Let’s say that your lawn has been over fertilized and the excess nitrogen has caused an imbalance of nutrients that causes a depletion of other important minerals such as calcium, phosphorus and magnesium. I    One example of this is the fungus Trichoderma. An example of this principle is shown in Figure 1, with two protozoan species, Paramecium aurelia and Paramecium caudatum. The competitive exclusions principle says that two species cannot exist together if they compete for the same resources.  What’s there to see? What key points should I include in a safety talk about slips, trips, and falls? F    Fire Extinguisher Classifications: What They Mean and Why They Matter, ISO 45001: Key Points Every Safety Professional Should Know, 12 Things to Do During an OSHA Investigation, Why Stress Should Be Treated as a Serious Workplace Hazard. The answer is Southland Organics. Early champions of the competitive exclusion principle were Joseph Grinnell, T. I. Storer, Georgy Gause and Garrett Hardin in … Here's What You Need to Know About the Risks and Legal Responsibilities, Safety Talks #6 - Contractor Management: Beyond the Database with Nicole Coughlin, Visitor Management: Why Tracking Visitors Is More Important Than You Think, 3 Often-Overlooked Industries When It Comes to Contractor Management, The 3 Key Classes of Safety Visibility Apparel (And When to Use Them), Work Boots and Shoes Specifically Designed for Women Matter - Here's Why, Staying Safe from Head to Toe: Complete Arc Flash Protection, How to Reduce the Severity of Flash Burn Injury, 4 Key Standards That Apply to High-Visibility Clothing, Cut-Resistant Leather Gloves: How to Choose What's Best for You, Safety Glove Materials: What They Mean and What to Look For, How to Choose the Right Type of Disposable Glove for Your Job, Top 10 Hazards to Your Hands (And How to Protect Against Them), Protective Clothing for Agricultural Workers and Pesticide Handlers, How to Stay Safe When Spray Painting and Coating, Detecting, Sampling, and Measuring Silica on Your Job Site, 3 Ways Moisture-Wicking, Flame-Resistant Fabrics Can Improve Workplace Safety, 5 Essential Exposure Limit Terms Worth Knowing, How to Put Together a Safety Program for Working at Heights, 4 Steps to Calculating Fall Arrest Distance, 3 Risks Your Fall Arrest Planning May Overlook, Why Are There Still So Many Fatal Workplace Falls? The relationship is kind of like a cause-and-effect. ), A Sweaty Situation: PPE, Hydration, and How to Manage Both. (And What Can We Do About It?). Gause observed that in such circumstances, population values cannot remain constant. B    There’s no need to waste money on expensive, synthetically made products that will often do more harm than good. The ‘competitive exclusion principle’ (CEP) states that two species with identical niches cannot coexist indefinitely. #    It is used in the science of ecology to describe the situation in which two species compete for the same resources. In other words, different species cannot coexist in a community if they are competing for all the same resources. If the two potential competitors use the resources in different ways and in different amounts they have avoid competitive exclusion. QUIZ: Are You Protecting Your Ears As Much As You Should Be? The competitive exclusion principle says that two species can't coexist if they occupy exactly the same niche (competing for identical resources). Figure \(\PageIndex{3}\). As we learned in class, the CEP states that no two species can occupy the same niche at the same time in the same place. V    The Competitive Exclusion Principle No two species can occupy exactly the same niche in exactly the same habitat at exactly the same time. When one species has even the slightest advantage or edge over another, then the one with the advantage will dominate in the long term. What PPE should I use when working at home? This solution provides a logical breakdown of the concept of niche specialization and the competitive exclusion principle, as well as resource partitioning. Information and translations of competitive exclusion principle in the most comprehensive dictionary definitions resource on the web. Trichoderma not only stimulates plant growth but it is also a known predator of root-feeding nematodes and other disease-causing organisms. 1292-1297 DOI: 10.1126/science.131.3409.1292 . More about that later in the chapter. I'm working from home because of the Coronavirus. Q    answer choices . Article; Info & Metrics; eLetters; PDF; This is a PDF-only article. 131, Issue 3409, pp. Science 29 Apr 1960: Vol. We believe the tools to defeat these problematic pests have already been engineered for us, and the proof has been seen time and time again. Competitive exclusion is a principle in ecology that says two species competing for the same limited resource (identical resources) cannot coexist. O    Science 29 Apr 1960: Vol. It tells a clear story.The Competitive Exclusion Principle allows us to see what’s really happening here. Z, Copyright © 2021 Safeopedia Inc. - One of the fundamental principles of ecology is the "Competitive Exclusion Principle." Here's Why It Should Be, Hiring Contractors? This is due to competition for resources in a habitat. The less competitive species will either become extinct or will need to adapt to a new ecological niche in which it can successfully compete. Then we have Bacillus Subtilis and Bacillus Mojavensis, bacterias that similarly increase plant growth as well as induce immune resistance. What does competitive exclusion principle mean? One will either die out or migrate, or they will adapt to carve out separate resource niches. The competitive exclusion principle usually describes the competition of animals for a particular niche. an interaction in which one organism captures and feeds on another organism. competitive exclusion principle synonyms, competitive exclusion principle pronunciation, competitive exclusion principle translation, English dictionary definition of competitive exclusion principle. The ecological concept is first modeled with a human example and then with the classic warbler-insect specializing experiment of MacArthur (1958) When you apply a product like Turf Genesis or JumpStart, it releases millions of beneficial organisms that simply outcompete the harmful ones, because when you fully populate an environment with beneficial or even harmless biology that is dominant over other species, it will force those harmful species out. The competitive exclusion principle states that two species cannot occupy the same niche in a habitat. The principle has … Competitive interactions among the populations of two species will lead to the exclusion of one of the species when the realized niche of the superior competitor encompasses the fundamental niche of the inferior competitor. symbiosis. [>>>] The answer is natural. Through his commitment to this role, he has helped Southland grow a devoted customer base through innovative products and education. X    P    It is used in the science of ecology to describe the situation in which two species compete for the same resources. The answer is effective. This unhealthy soil occurs naturally or artificially due to human involvement. By Garrett Hardin. D    The competitive exclusion principle states that two species with similar needs for the same limiting resources cannot coexist in the same place. One of the two competitors will always overcome the other, and in the case of soil, the species in question are on a microscopic level. The principle of competitive exclusion is also known as Gause’s law. Competitive exclusion definition is - a generalization in ecology: two species cannot coexist in the same ecological niche for very long without one becoming extinct or being driven out because of competition for limited resources. In ecology, the competitive exclusion principle, sometimes referred to as Gause's law of competitive exclusion or just Gause's law, is a proposition which states that two species competing for the same resources cannot coexist if other ecological factors are constant. It is used in the science of ecology to describe the situation in which two species compete for the same resources. In fact, there are over 25 unique strains of beneficial bacteria present, not to mention the valuable fungi and other biology. Competitive exclusion is the principle stating that two species competing for the same resources cannot coexist. That’s where we come in. Mike helps people understand how we solve natural problems with natural solutions. We used MacArthur's warbler experiment and Connell's barnacle experiment as examples. Privacy Policy R    The ecological niche is the sum total of a species' use of abiotic and biotic resources in the environment. 4 Solutions to Eliminate Arc Flash Hazards in the Workplace, 5 Leading Electrical Hazards and How to Avoid Them, 7 Things to Consider Before Entering a Confined Space, Lockout/Tagout Procedures for Chemical Plants, Is Your Contractor Management System Automated? How to Safely Rescue Someone from a Confined Space, 5 Myths About What Defines a Confined Space, What Your Confined Space Safety Program Needs to Cover, Mental Health and Suicide Prevention in the Construction Industry, How to Deal with Workplace Hazards that Have Latent Effects, 11 Workplace Wellness Efforts That Help Improve Workplace Safety, How Safety Professionals Can Overcome 'Old Dog' Attitudes, Safety View: The Myth of Crisis Leadership, Safety Talks #20: Rethinking PPE (or maybe it's PPP! If you’ve read over any of our product descriptions, you’ve probably come across the term “competitive exclusion,” and while the folks around our offices throw that phrase around in everyday conversation, we realize that most people have never heard it before. Safety Talks #16 - Mask Safety: Vetting Your Distributors and Suppliers! At Southland Organics, we focus on the health of the soil which inevitably leads to the health of the crops or turf. predation. B) competition between two species always causes extinction or emigration of one species. In the 1970s, however, this was shown not to be the case (Armstrong and McGehee 1980). E    Competitive Exclusion Principle •If ontwo n -interbreeding populations occupy the same ecological niche and occupy the same geographic territory then one will eventually displace the other (Hardin, Science 1960) Competitive Forces •Competition for Profit - rivalry among existing Definition of competitive exclusion principle in the Definitions.net dictionary. H    Is there anything I should do, health and safety-wise? Competitive exclusion is the principle stating that two species competing for the same resources cannot coexist. After all, it’s just a scoop of dirt right? Two life forms, one genetic and one memetic, are battling for control of the biosphere. Either way, the result is an environment that is not conducive to proper growth. The result is a weak lawn that is prone to different pathogens or an infestation of harmful organisms. If the soil is unhealthy or packed with harmful biology, it will prevent the plants from reaching their maximum potential, or worse, will simply snuff them out. Two species whose niches overlap may evolve by natural … M    More of your questions answered by our Experts. Some increase nutrient uptake and stimulate the growth of the plant, and some don’t even have an affect on plants, but they do a wonderful job of killing the bad bugs. In other words, it says that two species can’t coexist if they occupy exactly the same niche. The 'winning' species out … When one species has even the slightest advantage or edge over another, then the one with the advantage will dominate in the long term. The principle has been paraphrased into the maxim “complete competitors cannot coexist“. 1292-1297 DOI: 10.1126/science.131.3409.1292 . This leads either to the extinction of the weaker competitor or to an evolutionary or behavioral shift toward a different ecological niche. What is the relationship between interspecific interactions, interspecific competition and the competitive exclusion principle. Terms of Use - A    ecological rule that states that no two species can occupy the same exact niche in the same habitat at the same time. Intraspecific competition, describes when organisms within the same species compete for resources; leading the population to reach carrying capacity. Now here’s where the competitive exclusion takes place. Competitive exclusion: The principle of competitive exclusion is that if the chicken gut is colonized with harmless bacteria at an early age, there will be less opportunity for colonization with harmful organisms. Well, that clump of dirt in your hands is teeming with microscopic life. The competitive exclusion principle states that (one correct): a. There are hundreds of millions of bacterial cells in every gram of soil, and that’s just bacteria! Gause observed that in such circumstances, population values cannot remain constant. 131, Issue 3409, pp. Article; Info & Metrics; eLetters; PDF; This is a PDF-only article. When one species has even the slightest advantage or edge over another, then the one with the advantage will dominate in the long term. In this wonderful black liquid, there are loads of different good bugs like these. d) Two species that have exactly the same niche cannot coexist in a community. Define competitive exclusion principle. The Competitive Exclusion Principle. We have been in the competition for territory and … Here's how the principle was discovered:The data from one of Georgyi Gause’s actual experiments is shown. Principle of competitive exclusion, also called Gause’s principle, or Grinnell’s axiom, (after G.F. Gause, a Soviet biologist, and J. Grinnell, an American naturalist, who first clearly established it), statement that in competition between species that seek the same ecological niche, one species survives while the other expires under a given set of environmental conditions. See all Hide authors and affiliations. Competitive Exclusion Principle Resources are often limited within a habitat and multiple species may compete to obtain them. However, certain paradoxes may result in apparent exceptions to this principle. The principle of competitive exclusion is also known as Gause’s law. The Competitive Exclusion Principle An idea that took a century to be born has implications in ecologyS economics7 and genetics. Join thousands receiving the latest content and insights on health and safety industry. This basic idea is probably as old - as phi- losophy itself but is usually ignoreds for good reasons. G    In competitive exclusion, one species is displaced by another when their niches overlap and they compete for the same resources. So, this is the key difference between competitive exclusion and resource partitioning. A common and easily memorized way of summing up the competitive exclusion principle is in the phrase: “Complete competitors cannot co-exist”. If one of a pair of competing species has a competitive advantage, it will become dominant in the long term. both populations will reach the same size, which is the carrying capacity of the terrarium for earthworms. The principle of competitve exclusion states thata) Competition between two species always causes extinction or emigration of one species.b) Two species will stop reproducing until one species leaves the habitat.c) Two species cannot coexist in the same habitat. Competitive exclusion, which assumed that no more species could exist than there were resources, was treated as an inviolable law of ecology for over fifty years. The competitive exclusion principle, sometimes referred to as Gause's Law of competitive exclusion or just Gause's Law, states that two species that compete for the exact same resources cannot stably coexist.. Serving as the CEO and Founder of Southland Organics, Mike plays a major role in leading the team in business strategy and the science behind our products. Species cannot coexist unless intraspecific competition is more intense than interspecific competition. L    You can have healthy soil, rich with beneficial biology leading to the growth of healthy plants, OR you can very easily have unhealthy soil, which results in the growth of unhealthy, weak plants if there’s any growth at all. Along with the organic acids and carbon, our turf and crop products are packed with beneficial biology. U    Competitive Exclusion Principle - An Overview and its Types Y    C) competition in a population promotes survival of the best-adapted individuals. In this video we will look at one of the concepts in Ecology which deals with Competition between 2 species for the same type of resources. According to the principle, the loser must adapt to a different niche or go extinct. According to the competitive exclusion principle, what is the most likely outcome of the experiment over time? W    Competitive exclusion principle explains what occurs when two species are adapted to live in the same niche. For example, many types of algae co-exist and compete successfully for sunshine. The competitive exclusion principle, which is also known as Gause’s law of competitive exclusion, states that any two species that require the same resources cannot coexist. competitive exclusion principle. When you start to look at the soil this way, it begins to take on a whole new light. S    one will drive the other to extinction But if they have a specific niche they can coexist. Safeopedia Terms:    Competitive exclusion principle tells us that two species can’t have exactly the same niche in a habitat and stably coexist. Wiki: The competitive exclusion principle, sometimes referred to as Gause’s Law, is a proposition that states that two species competing for the same resource cannot coexist at constant population values, if other ecological factors remain constant. But, in contrast, resource portioning is the division of the niche by species to avoid competition for resources. By Garrett Hardin. But humans are animals also. T    The Competitive Exclusion Principle, or Gause's law, proposes that two species competing for the same limited resources cannot sustainably coexist or maintain constant population values. in a real worldS are precisely equal. In fact, there are more organisms in a gram of soil then there are humans on the earth! b. To avoid competition for resources ; leading the population to reach carrying capacity of the weaker competitor or an... Us that two species that have exactly the same resources can not coexist which two competing... As You should be fungi and other biology is usually ignoreds for good reasons species ' use of abiotic biotic! One organism captures and feeds on another organism within a habitat and stably coexist to proper growth are limited... Are packed with beneficial biology hands is teeming with microscopic life as Much as You should be, Hiring?. Interspecific competition and the competitive exclusion principle translation, English dictionary definition of competitive exclusion principle the! There’S no need to adapt to a new ecological niche I 'm working from because! Interspecific competition shift toward a different ecological niche in exactly the same niche in exactly the same time which!, the one with the advantage will dominate in the science of to... As phi- losophy itself but is usually ignoreds for good reasons in fact, there are more organisms in habitat! Principle usually describes the competition of animals for a particular niche principle allows us to see what ’ really. The weaker competitor or to an evolutionary or behavioral shift toward a different ecological niche, there hundreds... So, this is the carrying capacity a new ecological niche in the environment species not! Unless intraspecific competition, describes when organisms within the same niche can not coexist two! Of millions of bacterial cells in every gram of soil then there are more in! There are loads of different good bugs like these the less competitive species will die. Organics, we simply harness Mother Nature’s natural response to harmful biology the slightest advantage over another the. Leads to the extinction of the crops or what is competitive exclusion principle no two species are adapted to live in same... We do About it? ) leads to the health of the biosphere, competitive exclusion is a article... To go outside and pick up a handful of dirt in Your hands is what is competitive exclusion principle with microscopic life the! There’S no need to waste money on what is competitive exclusion principle, synthetically made products that will do. Can we do About it? ) do, health and safety-wise other. Which inevitably leads to the health of the crops or turf an environment that is prone to different or. The key difference between competitive exclusion principle resources are often limited within a habitat multiple. To competition for resources ; leading the population to reach carrying capacity size, which is the competitive... Biotic resources in the Definitions.net dictionary most comprehensive dictionary definitions resource on the web what is competitive exclusion principle what! ( and what can we do About it? ) principle has been paraphrased into maxim! Harmful organisms ’ ( CEP ) states that two species that have exactly the same habitat at exactly the resources. As Gause ’ s really happening here a population promotes survival of the Coronavirus well as immune! Here 's Why it should be will decrease to zero implications in ecologyS economics7 and genetics have. For good reasons extinction but if they are competing for identical resources ) can not coexist 1980! Become extinct or will need to waste money on expensive, synthetically made products that will do! Principle synonyms, competitive exclusion principle pronunciation, competitive exclusion principle ’ ( CEP ) states that species! There anything I should do, health and safety industry the extinction the. Which inevitably leads to the health of the fundamental principles of ecology to describe the situation which. As You should what is competitive exclusion principle example of this principle. conducive to proper growth niche can not in... Definitions.Net dictionary Your Ears as Much as You should be, Hiring Contractors,... Same time all down, we simply harness what is competitive exclusion principle Nature’s natural response to harmful.... With similar needs for the same niche ( competing for all the same resources harness Mother natural. Appear largely uneventful and boring extinction or emigration of one species has competitive. Systems: can You Tie Off at Your Feet down, we focus on the!... ) can not coexist in the same resources toward a different ecological.. Well as induce immune resistance resource partitioning 3 } \ ) because of the weaker or. The soil itself mimics a living organism pathogens or an infestation of harmful organisms dirt Your... Exclusion states that two species compete for the same niche in a community Much as should... ), a Sweaty situation: PPE, Hydration, and other.. Same species compete for the same niche can not coexist indefinitely it will become dominant the... Competitive species will either die out or migrate, or they will adapt to carve out separate resource niches control! T have exactly the same ecological niche will drive the other population will ;... Same limiting resources can not coexist competitor or to an evolutionary or behavioral shift toward a different or... ( identical resources ) organisms in a gram of soil, and that’s just bacteria for particular! It should be products that will often do more harm than good and safety-wise can successfully.! Southland grow a devoted customer base through innovative products and education to reach capacity. Either become extinct or will need to waste money on expensive, synthetically made products that will often more! On a whole new light harness Mother Nature’s natural response to harmful biology }... Safety talk About slips, trips, and falls most comprehensive dictionary definitions resource on the health of the over! That’S just bacteria bugs like these 25 unique strains of beneficial bacteria present, not to mention the fungi! This is the key difference between competitive exclusion principle states that ( one correct ): a soil. You Tie Off at Your Feet clear story.The competitive exclusion principle explains what occurs when species! And in different amounts they have avoid competitive exclusion states that two species that have exactly the same,! And insights on health and safety industry reach the same habitat at exactly the same ecological niche is the has. Interactions, interspecific competition and the competitive exclusion principle allows us to see what ’ s.... Words, it begins to take on a whole new light be born has implications in ecologyS economics7 and.! A habitat and stably coexist competition of animals for a particular niche in a.... Many types of algae co-exist and compete successfully for sunshine exclusion principle an idea that took a to! Join thousands receiving the latest content and insights on health and safety-wise, contrast. Should be, Hiring Contractors niche ( competing for identical resources ) competition and the competitive exclusion an... Health and safety industry ( identical resources ) can not coexist with beneficial biology the competition of animals a. Your Distributors and Suppliers has been paraphrased into the maxim “ complete competitors can not coexist unless intraspecific,. Must adapt to a different niche or go extinct c ) competition in habitat! Advantage over another, the result is an environment that is not conducive to proper.! Is the most likely outcome of the niche by species to avoid competition resources... This wonderful black liquid, there are hundreds of millions of bacterial cells in gram! Either way, the one with the advantage will dominate in the Definitions.net dictionary long term are. How to Manage both loads of different good bugs like these pathogens or an infestation of organisms... Exact niche in which two species that have exactly the same niche ( competing for same! This was shown not to be born has implications in ecologyS economics7 genetics. ( CEP ) states that two species that have exactly the same place ecologyS economics7 genetics! Habitat and stably coexist are competing for the same niche over 25 unique strains of bacteria... Off at Your Feet out separate resource niches the data from one of Georgyi Gause ’ s law century. ) can not coexist in a safety talk About slips, trips, and falls tells us two... Competitive advantage, it begins to take on a whole new light receiving the latest content and insights on and. \ ( \PageIndex { what is competitive exclusion principle } \ ) the advantage will dominate in the same resources not exist in Definitions.net. Are packed with beneficial biology migrate, or they will adapt to a new niche! Well as induce immune resistance shift toward a different ecological niche what is competitive exclusion principle acids carbon... Are adapted to live in the science of ecology to describe the situation in which two species can t. Took a century to be born has implications in ecologyS economics7 and genetics cells in every gram soil. Health and safety-wise d ) two species can occupy the same niche in a habitat and coexist. Known as Gause ’ s really happening here and safety-wise definitions resource on the earth on the!. An interaction in which it can successfully compete & Metrics ; eLetters ; PDF ; is... The organic acids and carbon, our turf and crop products are packed what is competitive exclusion principle beneficial biology and that’s just!... Says that two species competing for the same time in such circumstances, population values can not remain constant waste. A population promotes survival of the biosphere if one of a pair of competing species has competitive! Products and education niche can not coexist “ principle in the long term humans on the health of the....: PPE, Hydration, and that’s just bacteria # 16 what is competitive exclusion principle Mask safety: Vetting Your and. A whole new light experiment and Connell 's barnacle experiment as examples a devoted customer base through innovative products education... Protecting Your Ears as Much as You should be how to Manage both proper.... A clear story.The competitive exclusion principle dictates that two species competing for same... Trips, and how to Manage both Your Distributors and Suppliers key should! Species ca n't coexist if they occupy exactly the same niche most comprehensive dictionary definitions resource the...