A key term in ecology is 'ecosystem'. Examples of bad definition of ecosystem: These are two definitions of ecosystem that can be found in Internet: 1. "a system formed by the interaction of a community of organisms with their physical environment" (see: wordnetweb.princeton.edu/perl/webwn) The drawbacks of this definition: another term is used , namely, 'community'; why only physical environment is mentioned? if you mention 'physical', you are to mention 'chemical' one as well... 2. "An ecosystem is a complex set of relationships among the living resources, habitats, and residents of an area. It includes plants, trees, animals, fish, birds, microrganisms, water, soil, and people". http://forest.mtu.edu/kidscorner/ecosystems/definition.html The drawbacks of this definition: another term is used , namely, 'habitats'; why only 'living resources' are mentioned? if you mention 'living resources' , you are to mention non-living as well... ; it is wrong to list 'animals, fish, birds, ' (as 'fish' and 'bird' are part of the general term 'animals'); by the same token, it is wrong to list 'plants, trees,...' (as 'trees' are part of the general term 'plants') . That is why it is important that an attempt was made to give a better definition. An example of such attempt see: http://blog.researchgate.net/masterblog/2220_New_Definition_of_Ecosystem; (in English); http://scipeople.com/publication/99205/; (in Russian); http://scipeople.com/publication/70259/; (in Russian); http://scipeople.com/publication/66938/ (in Russian) Also see the paper: Ostroumov S.A., New definitions of the concepts and terms ecosystem and biogeocenosis. — Doklady Biological Sciences. 2002. Vol. 383: 141-143. 2 tables. Bibliogr. 15. [Publisher: MAIK Nauka / Interperiodica distributed exclusively by Springer Science+Business Media LLC.] ISSN 0012-4966 (Print) 1608-3105 (Online). DOI 10.1023/A:1015393924967. http://www.springerlink.com/content/vpg4yu2v3yd6t97b/ In 1935 the term 'ecosystem' was coined by A. Tansley. In the 1940s, another important term, 'biogeocoenosis', was introduced by V. N. Sukachev. Since that time, a lot of new facts have accumulated in ecology. It is necessary to revisit the formulation of the basic concepts and terms in ecology, including the two terms mentioned above. The author proposed some new variants of the definition of the two terms that (1) reflect the modern vision of the basics of ecology; and (2) avoid the vicious circle of using other terms that in turn request their require definitions. The author realizes that the new variants of the terms cannot be ideal and some other variants of the definitions are also possible. Tables: 5 specific features of the proposed definition of ecosystem (Table 1); 8 specific features of the proposed definition of biogeocenosis, and 8 distinctions between the proposed definition and the classical definition by V.N.Sukachev (Table 2). Aslo see: Ecological concepts "ecosystem", "biogeocenosis", "ecosystem boundaries": search for new definitions. – Moscow University Biological Sciences Bulletin. 2003. Vol. 58. No. 3. P.29-38. Tab. Bibliogr. 44 refs. [ISSN 0096-3925; Publisher: Allerton Press, Inc., 18 West 27th Street, N.Y., NY 10001].