1. Lexicology as a branch of linguistics. Lexical units

16. Phraseological units
Phraseological units are comparatively stable and semantically inseparable. The essential features of phraseological units are stability of the lexical components and lack of motivation.
The interpretation of the phraseology in Engl.

• 
  a way of expressing oneself
  
• 
  a way in which words and phrases are used especially by particular individuals and group of individ.
  

Features:

• 
  they are ready-made unit
  
• 
  they are characterised by stability of grammatical structure and lexical components
  
• 
  they are idiomatic, transferred. They are colourful, expressive, stylistically marked.
  

The debatable problems:

1. 
   the problem of the adequate term and its definition ( The definition is felt to be inadequate as the concept ready- made units seems to be rather vague. In fact this term can be applied to a variety of heterogeneous linguistic phenomena ranging from word-groups to sentences (e.g. proverbs, sayings, collocation, lexical phrases) and also quotations from poems, novels or scientific treatises all of which can be described as ready-made units)
   
2. 
   the problem of the lang. material which is reflected to phraseology ( narrow and wide approaches in phraseology: some scholars used term word equivalents instead of phrasal units. This narrow understanding. Now many scholars expand a wide approach to phraseology and they include in the phraseologycal sentence idioms, proverbs, saying, clause idioms).
   

3.the problem of the classification of the lang. material (classification of Vinogradova: Phraseological fusions(сращения) are completely non-motivated word-groups, such as red tape — ‘bureaucratic methods’; heavy father — ’serious or solemn part in a theatrical play’; kick the bucket — ‘die’; and the like. The meaning of the components has no connections whatsoever, at least synchronically, with the meaning of the whole group.
Phraseological unities are partially non-motivated as their meaning can usually be perceived through the metaphoric meaning of the whole phraseological unit. For EG: to skate of thin ice – рисковать; to sit on the fence – выжидать; a big bug – важная шишка.
Phraseological collocations are motivated but they are made up of words possessing specific lexical valency which accounts for a certain degree of stability in such word-groups. In phraseological collocations variability of member-words is strictly limited.