On the example of the concepts of «lawn», «phytocoenosis», «ecology» outlines the general laws of the gradual transformation of foreign-language professional word in the scientific term. It is proposed the following definition of the latter concepts. Ecology is a science about relationships of an organism or community of organisms with environmental factors (natural and anthropogenic). The process of formation of a new term, its approval as a full and irreplaceable in the professional language as well as the accuracy and appropriateness of the use will be more clear and expressive, if they come from an analysis of the concept of niche terminology. These words («terminological niche») is called a set of practical and scientific factors that provide or may provide a normal appearance and communicative functioning of the term. Under «normal functioning» of the term we mean the state of its constant use in any style and genre of contemporary normative language understood by the reader according to the signified concept. The proposed understanding of the terminological niche allows in readable position to see the rule that each term pass through the following stages of its development. 1. Free terminological niche stage. At this time, there is no any name of the material or intellectual object (object, phenomenon, point of view, and so on) after the formation of it in reality or in the mind of the author. Between the cause (the appearance of the object) and the effect (the formation of its name), there is a time gap that exists within minutes, but can last for years. 2. Stage of filling the free terminological niche (formation of the term). This time is characterized, among other things, by the existence of professional words mostly as synonymous new object names with their «desire» to leave (as a result of competitive relations of different professional words) to the level of a full indispensable term within the normative language and the specific term system. At the beginning of this stage of professional words (the term precursors) can be used in the narrow circle of specialists or be banned. This is the primary latent (hidden) state of the term. 3. The stage completely filled a niche – during the maturity of the term, its stay at the height of the functional capacity, the situation is universal acceptance of relevant specific of the term designated of its concept. 4. Step regressive niche is time of regression, degradation of the term, which is manifested, among other things, to homonymy, secondary synonymy, reducing in the frequency of use of the term in written and oral texts. 5. Stage of dead niche. The situation is of exhaustion factors that ensure the normal funtioning of the term and the lack of its use in texts. The ability to save the historical meaning of the term indicates the presence of a secondary latent niche. The adjustments in the above-proposed scheme can make cases of return the names of the past and rename concepts. It is shown that the terms are characterized by emotional and expressive component at all stages of their existence. The intensity of expression varies from a minimum periodic manifestations to the maximum expressiveness, which can significantly distort the content of the concept, as is often the case with the term «ecology».