The article deals with the description of a word form po idee, which has been exposed to the processes of lexicalization and pragmaticalization both in colloquial and written speech. These processes can lead to forming new words or extension in functions and meaning of words that already exist and the changes are rarely represented in dictionaries and grammar references. The research has shown that the word form po idee has considerable pragmatic potential in colloquial speech after separation from noun paradigm. This article represents an attempt to analyze its role in lowering of the categoricity of the utterance and, moreover, there are taken into consideration its further transformations in spontaneous speech, such as appearance of modal meaning, the possibility to use it as an analogue of a conjunctive or as a reflexive. Analysis is based on the material, provided by two corpuses of speech: spoken subcorpus of the Russian National Corpus and “One Speaker’s Day” in order to represent actual transformation in semantics and functions of the word form po idee in modern Russian language. The results of this research can be used not only for creating adequate description of current status of Russian language, but also for description of Russian native speakers’ conversation practice.