The essence of translation theory can – generally – be treated as establishment or clarification of different relations between the language of the original and the language of the translation. Accordingly, language variance is related to the linguistic units which are formally different but function identically or, in turn, there is a different phonological, morphological, sintactic, phraseological and textual realization of one and the same unite.

Two analysis approaches derived from two types of variance can be distinguished in relation to the variance in translation theory. The first, interlinguistic – outside of the language, occurs within the borders of one language, and the second refers to the relations between the language of the original, source text, for example English, and the other languages in which the text is being translated, e.e. Polish or Macedonian. The immanent properties in theory of translation apply to the first approach, as well as the second one, and they can be accompanied by the phenomena of equivalence and adequacy.

The phenomenon of equivalence in the theory of translation was observed by E. Nida, who devived equivalence to formal and functional equivalence. Functional equivalence (or dynamic equivalence) conveys the main idea expressed in the source text. If necessary, that goal can be achieved at the expense of the literality of the original (what we have in the original as a form, transferred by another form in literal sense), as well as the word order in the sentence or the grammatical form of the source text. According to the formal equivalence, the text of the original and the translation are treated literally, “word for word” (verbum pro verbum).

The difference between the variance of the translation and the equivalence – although the first and second appear at all levels of the original language (OL) and the translation (LT), yet, their scope is different: the first (variance) refers to, to several degrees, different equivalent (grammatical, lexical, stylistic) language versions of the translation. In case of the second, equivalence only basically connects the two languages – the language of the original and the language of the translation – and, yet, the connection is present on all language structure levels.