iomatic expressions. In between these two cate- gories there is a vast layer of the so called set phrases institutionalized as such in the language and originated owing to the ability of words to regularly link up with other words forming their lexical environment. Whereas their global mean- ings are readily grasped from the meanings of their component parts, relatively independent of each other and used in their literal or metaphorical sense, the meanings of idiomatic expressions proper often appear unmotivated and cannot be deduced from the meanings of their constituents. As regards the degree of their structural mobility, idiomatic expressions are generally more or less invariable in form or order and do not admit of the usual grammatical op- erations which their literal counterparts will per- mit. Other types of phrases normally show some degree of variation. Phrases making up the dic- tionary are just as heterogeneous syntactically: some of them are full sentences (catch phrases, proverbial expressions, rhetorical questions and social formulae) while others function like par- ticular parts of speech (nominal, verbal, ad- verbial and adjectival phrases). Phraseological units whose meanings may mistakenly appear similar or opposite can be re- duced to the following principal types of inter- ferentially relevant oppositions (in the order of diminishing similarity of their notional compo- nents): specific cases of phraseological polysemy or homonymy when formally identical units are used differently by British and American speakers, e.g.: pavement artist (UK) pavement artist (US) • semantically dissimilar units with identical notional components, relating as pseudo- quantitative variants, when one of the phrases is not really just a shortened form of an ex- tended phrase, e.g.: keep one’s head keep one’s head up • semantically dissimilar units all of whose no- tional components are identical, e.g.: cut loose from something cut loose with something • phrases forming semantic oppositions to anal- ogous solidly spelled compounds, e.g.: black eye blackeye • morphologically consonant, though unrelated place names, e.g.: Saint John’s Saint Johns • semantically dissimilar prepositional phrases with identical notional component preceding the preposition, e.g.: absent from something absent in something • semantically dissimilar prepositional phrases with identical notional component following the preposition, e.g.: in time on time • semantically distinct phrasal verbs with iden- tical verbal component, e.g.: turn on someone turn to someone • semantically dissimilar collocations with iden- tical verbal component taking direct and pre- positional object respectively, e.g.: advertise for something advertise something • semantically dissimilar units some of whose components are identical while others relate as paronyms, e.g.: historic event historical event • semantically dissimilar units with paronymic and identical notional components, which be- long to different parts of speech, e.g.: curtain raiser raise the curtain • semantically dissimilar units some of whose components are identical while others relate as synonyms, e.g.: hold an appointment keep an appointment –5– Introduction