It is important to realize that idioms are not only colloquial expressions, as many people believe. They appear in formal style and in slang, in poetry, in the language of Shakespeare and the Bible. What then is an idiom? An idiom can be defined as a number of words which, when taken together, have a different meaning from the individual meanings of each word.
Where and when to use idioms
One of the main difficulties for learners is knowing in which situations it is correct to use an idiom, i.e. the level of style. Unmarked idioms are neutral and may be used in most situations. Informal idioms are used in everyday spoken English and in personal letters. Learners are advised to avoid using slang and taboo expressions until their mastery of the language is complete. Several examples are, however, included for reference purposes.
A further difficulty is knowing whether an idiom is natural or appropriate in a certain situation. Examples of typical use in particular situations, such as in business contexts, are given and these should be studied carefully.
Another difficulty is that of fixed idioms and idioms with variants. It is most important to be exact in one’s use of fixed idioms, as an inaccurate idiom may mean nothing to a native speaker. Above all, remember that it is extremely unwise to translate idioms into or from one’s native language. One may be lucky that the tv-o languages have the same form and vocabulary, but in most cases, the result will be utterly bewildering to the English native speaker — and possibly highly amusing.