Phraseological units are habitually defined as non-motivated word-groups that cannot be freely made up in speech but are reproduced as ready-made units. Thus, for example, the constituent redin the free word-group red flowermay, if necessary, be substituted for by any other adjective denoting colour (blue, white,etc.), without essentially changing the denotational meaning of the word-group under discussion (a flower of a certain colour). In the phraseological unit red tape(bureaucratic “methods) no such substitution is possible, as a change of the adjective would involve a complete change in the meaning of the whole group. A blue (black, white,etc.) tapewould mean ‘a tape of a certain colour’. It follows that the phraseological unit red tapeis semantically non-motivated, i.e. its meaning cannot be deduced from the meaning of its components and that it exists as a ready-made linguistic unit which does not allow of any variability of its lexical components.
Phraseological units in Modern English are also approached from the contextual point of view. Proceeding from the assumption that individual meanings of polysemantic words can be observed in certain contexts and may be viewed as dependent on those contexts, it is argued that phraseological units are to be defined through specific types of context. Free word-groups make up variable contexts whereas the essential feature of phraseological units is a non-variable or fixed context.‘ Non-variability is understood as the stability of the word-group.
The two criteria of phraseological units — specialised meaning of the components and non-variability of context — display unilateral dependence. Specialised meaning presupposes complete stability of the lexical components, as specialised meaning of the member-words or idiomatic meaning of the whole word-group is never observed outside fixed contexts.
Phraseological units may be subdivided into phrasemes and idioms according to whether or not one of the components of the whole word-group possesses specialised meaning.
Phrasemes are, as a rule, two-member word-groups in which one of the members has specialised meaning dependent on the second component as, e.g., in small hours;the second component (hours)serves as the only clue to this particular meaning of the first component as it is found only in the given context (small hours).The word that serves as the clue to the specialised meaning of one of the components is habitually used in its central meaning (cf., for example, small hours,and three hours, pleasant hours,etc.).
Idioms are distinguished from phrasemes by the idiomaticity of the whole word-group (e.g. red tape — ‘bureaucratic methods’) and the impossibility of attaching meaning to the members of the group taken in isolation. Idioms are semantically and grammatically inseparable units. They may comprise unusual combinations of words which when understood in their literal meaning are normally unallocable as, e.g. mare’s nest (a mare — ‘a female horse’, a mare’s nest — ‘a hoax, a discovery which proves false or worthless’). Unusualness of collocability, or logical incompatibility of member-words is indicative of the idiomaticity of the phrase.
Idioms made up of words normally brought together are homonymous with corresponding variable word-groups, e.g. to let the cat outof the bag — ‘to divulge a secret’, and the clue to the idiomatic meaning is to be found in a wider context outside the phrase itself.