something entirely new and far removed from the current meanings of the constituents.
Academician V. V. Vinogradov spoke of the semantic change in phraseological units as "a meaning resulting from a peculiar chemical combination of words". This seems a very apt comparison because in both cases between which the parallel is drawn an entirely new quality comes into existence.
The semantic shift affecting phraseological units does not consist in a mere change of meanings of each separate constituent part of the unit. The meanings of the constituents merge to produce an entirely new meaning: e. g. to have a bee in one's bonnet means "to have an obsession about something; to be eccentric or even a little mad". The humorous metaphoric comparison with a person who is distracted by a bee continually buzzing under his cap has become erased and half-forgotten, and the speakers using the expression hardly think of bees or bonnets but accept it in its transferred sense: "obsessed, eccentric".
That is what is meant when phraseological units are said to be characterised by semantic unity. In the traditional approach, phraseological units have been defined as word-groups conveying a single concept (whereas in free word-groups each meaningful component stands for a separate concept).
It is this feature that makes phraseological units similar to words: both words and phraseological units possess semantic unity (see Introduction). Yet, words are also characterised by structural unity which phraseological units very obviously lack being combinations of words.
Most Russian scholars today accept the semantic criterion of distinguishing phraseological units from free word-groups as the major one and base their research work in the field of phraseology on the defini-