Reasoned and unmotivated terminological units of oil and gas terms in structure of the concept of «Petroleum» (on the material of modern English)

The present article deals with the problem of non-fixed position of terminological units in the structure of the given concept. The position of the terms in the structure of the concept is determined by the category of the level of their motivation or non-motivation, where the latter, being a subjective category, is unique for every speaking person. Terms can move from one part of the concept to another one, a strictly fixed position does not exist.