The monograph examines the poetic language of Boris Pasternak's book "My Sister is Life" through the prism of idiomatics (collocations, phraseological units, stable phrases, constructions and sayings). A close reading of the poems of the collection - from the analysis of individual lines and stanzas to the linguistic analysis of several poems - suggests that the "ready" phrases were a source of unexpected and dark metaphors for the poet, and also provided increased semantic connectivity and ambiguity of the poetic text. The special role of idiomatics in "My Sister - Life" makes it possible to address the problem of the evolution of the poetic language of modernism on new grounds.