The problems of studying the lexical structure of a word have a way out into various areas of cognitive science, including biosemiotics. In the article, the biosemiotic approach is reframed into a biosemantic approach based on decoding specific lexical structures. The lexical invariants of polysemous words are shown to be meaningful cores of their figurative meanings. It is a set of dominant semantic components that are stably associated with each lexeme’s meaning. In the process of semiosis, the individual is guided by these invariant components. These components are formed over time in the individual's cognitive niche as a result of observations of the relationship between language signs. The practical part of the article includes an empirical invariant-component analysis of the English polysemous substantive “a hood” from the standpoint of invariant semantics. Given the results, biosemiotics has an advantage over traditional semantics in describing the semantics of lexical units.