The vocabulary of a language is enriched not only by words but also by phraseological units. Phraseological units are word-groups that cannot be made in the process of speech they exist in the language as ready-made units. They are stable word-groups characterized by a completely or partially transferred meaning and compiled in special dictionaries. The same as words phraseological units express a single notion and are used in a sentence as one part of it. American and British lexicographers call such units «idioms». We can mention such dictionaries as: L.Smith «Words and Idioms», V.Collins «A Book of English Idioms» etc. In these dictionaries we can fi nd words, peculiar in their semantics (idiomatic), side by side with word-groups and sentences. In these dictionaries they are arranged, as a rule, into different semantic groups. Idioms are widely used in standard spoken and written English today and can be defi ned as established and essential speech units with fi xed and constant structures.

An idiom is a combination of words having a meaning that is different from the meanings of the individual words themselves. It is a phrase which does not always follow the normal rules of meaning and grammar. The famous linguist J.S. McMordie says that “many idioms are examples of strong collocations, for example it is diffi cult to see why

spill the beans should mean (to give away secret information).The words and grammar that make up this idiom are almost impossible to change, without changing the meaning” [McMordie, 2000: 352].

E.g.: To sit on the fence – can literally mean that one is sitting on a fence. However, the idiomatic meaning of this phrase is “that one is not making a clear choice regarding some issue”. Many idioms are unique and fi xed in their grammatical structure. The expression to sit on the fence cannot become “to sit on a fence” or “to sit on the fences”. Phraseological units, or idioms, as they are called by most western scholars, represent the most colourful and expressive part of the language’s vocabulary. It refl ects the nation’s customs, facts, tradition of the past history. E.g.: Dark horse – actually not a horse but a person about whom no one knows anything defi nite and so one is not sure what can be expected from him. It is connected with the British tradition to go horse races and bid as to what horse can win the race. Often the race is won by an unknown horse, hence the expression dark horse.

E.g.: A white elephant is a valuable object or a thing which involves great expense or trouble for its owner, it may have cost a lot of money and which is also diffi cult to dispose of. Eg.: The new offi ce block has become an expensive white elephant. This phrase came from the interesting story, when the king of Siam (now Thailand) presented such elephants to the people whom he didn’t like and wanted to ruin them. That person would have to spend all their money on looking after the rare animal and of course it was very expensive to have these animals in the household.