The article shows how language consciousness forms semantic unities and individualities in its mental lexicon. The article typologies and lists the functions of indeterminacy markers in English and Russian. The category of indeterminacy is juxtaposed to the problem of polysemous word representation at the lexicon level. We focus our attention on the contextless general representative of a polysemous word's structure, called its "lexical invariant". The invariant is a generalized experience of the word's contextual realizations, narrowing its semantic components to dominant and stable necessary minimums that stand behind conceptualization and formation of new meanings. Empirical invariant-component analysis of English polysemous words “a leg”, “a cheek”, “a knee” serve as examples of the invariant's functioning. The analysis allowed us to determine the invariants of these words as collections of base dominant components of a word's semantic nucleus. In speech context, an invariant takes shape as one of its combinatorial variants.