Phraseological units can be classified according to the degree of motivation of their meaning. There are three types of phraseological units:

• a) fusions – where the degree of motivation is very low, we cannot guess the meaning of the whole from the meanings of its components, they are highly idiomatic and cannot be translated word for word into other languages, e.g. at sixes and sevens (means in a mess).
• b) unities – where the meaning of the whole can be guessed from the meanings of its components, but it is transferred (metaphorical or metonymical), e.g. to play the first fiddle (to be a leader in something), old salt (experienced sailor), etc.
• c) collocations – where words are combined in their original meaning but their combinations are different in different languages, e.g. cash and carry (self-service shop, in a big way (in great degree), etc.