The phonemes in isolation have no meaning, but they constitute morphemes and words, all of which are meaningful.
The phoneme, its definition, aspects and functions
The functions of the phoneme:
3) recognitive (identificatory)
(распознавательная)
This function of the phoneme consists in making words with their grammatical forms easily recognizable as a result of the use of right allophones in their right places.
A phoneme is defined by him as a group of related (родственный) sounds of a given language which are so used in connected speech that no one of them ever occurs in the position which any other can occupy.