Prof. A.I. Smirnitsky worked out structural classifi cation of phraseological units, comparing them with words. He points out onetop units which he compares with derived words because derived words have only one root morpheme. He points out two-top units which he compares with compound words because in compound words we usually have two root morphemes. Among one-top units he points out three structural types;

a) units of the type «to give up» (verb + postposition type), e.g. to art up, to back up, to drop out, to nose out, to buy into, to sandwich in etc.; b) units of the type «to be tired» . Some of these units remind the Passive Voice in their structure but they have different prepositions with them, while in the Passive Voice we can have only prepositions «by» or «with», e.g. to be tired of, to be interested in, to be surprised at etc. c) prepositional – nominal phraseological units. These units are equivalents of unchangeable words: prepositions, conjunctions, adverbs, that is why they have no grammar centre, their semantic centre is the nominal part, e.g. on the doorstep (quite near), on the nose (exactly), in the course of, on the stroke of, on time, in time, on the point of etc. Among two-top units A.I. Smirnitsky points out the following structural types: a) attributive-nominal such as: a month of Sundays, grey matter, a millstone round one’s neck and many others. Units of this type are noun equivalents and can be partly or perfectly idiomatic. In partly idiomatic units (phrasisms) sometimes the fi rst component is idiomatic, e.g. high road, in other cases the second component is idiomatic, e.g.

fi rst night. In many cases both components are idiomatic, e.g. red tape, blind alley, bed of nail, shot in the arm and many others.

b) verb-nominal phraseological units, e.g. to read between the lines, to sweep under the carpet etc. The grammar centre of such units is the verb, the semantic centre in many cases is the nominal component, e.g. to fall in love. In some units the verb is both the grammar and the semantic centre, e.g. not to know the ropes. These units can be perfectly idiomatic as well, e.g. to burn one’s boats, to vote with one’s feet, to take to the cleaners’ etc. c) phraseological repetitions, such as: now or never, part and parcel , country and western etc. Such units can be built on antonyms, e.g. ups and downs, back and forth; often they are formed by means of alliteration, e.g. cakes and ale, as busy as a bee.