In language studies there are two very clearly-marked tendencies that the student should never lose sight of, particularly when dealing with the problem of word-combination. They are 1) the analytical tendency, which seeks to dissever one component from another and 2) the synthetic tendency which seeks to integrate the parts of the combination into a stable unit.
These two tendencies are treated in different ways in lexicology and stylistics. In lexicology the parts of a stable lexical unit may be separated in order to make a scientific investigation of the character of the combination and to analyse the components. In stylistics we analyse the component parts in order to get at some communicative effect sought by the writer. It is this communicative effect and the means employed to achieve it that Jie within the domain of stylistics.
The integrating tendency also is closely studied in the realm of lexicology, especially when linguistic scholars seek to fix what seems to be a stable word-combination and ascertain the degree of its stability, its variants and so on. The integrating tendency is also within the domain of stylistics, particularly when the word-combination has not yet formed itself as a lexical unit but is in the process of being so formed.
Here we are faced with the problem of what is called the cliche.