ferred meaning show the weakest cohesion between their components. The more distant the meaning of a phraseological unit from the current meaning of its constituent parts, the greater is its degree of semantic cohesion. Accordingly, Vinogradov classifies phraseological units into three classes: phraseological combinations, unities and fusions (R. фразеологические сочетания, единства и сращения). 
Phraseological combinations are word-groups with a partially changed meaning. They may be said to be clearly motivated, that is, the meaning of the unit can be easily deduced from the meanings of its constituents.
E. g. to be at one's wits' end, to be good at something, to be a good hand at something, to have a bite, to come off a poor second, to come to a sticky end (coll.), to look a sight (coll.), to take something for granted, to stick to one's word, to stick at nothing, gospel truth, bosom friends.
Phraseological unities are word-groups with a completely changed meaning, that is, the meaning of the unit does not correspond to the meanings of its constituent parts. They are motivated units or, putting it another way, the meaning of the whole unit can be deduced from the meanings of the constituent parts; the metaphor, on which the shift of meaning is based, is clear and transparent.
E. g. to stick to one's guns (~ to be true to one's views or convictions. The image is that of a gunner or guncrew who do not desert their guns even if a battle seems lost); to sit on the fence (~ in discussion, politics, etc. refrain from committing oneself to either side); to catch/clutch at a straw/straws (~ when in extreme danger, avail oneself of even the slightest chance of rescue); to lose one's head (~ to be at a loss what to do; to be out of one's mind); to lose one's heart to smb. (~ to fall in love); to lock the stable door after the horse is stolen (~ to take precautions too late, when