Lexis meaning ‘word, phrase’ (hence lexicos ‘having to do with words’) and logos

Ex. to beg and beggar
Synchronically, the words to beg and beggar are related as a simple and a derived word, the noun beggar being the derived member of the pair, for the derivative correlation between the two is the same as in the case of to sing — singer, to teach — teacher, etc. When we approach the problem diachronically, however, we learn that the noun beggar was borrowed from Old French and only presumed to have been derived from a shorter word, namely the verb to beg, as in the English language agent nouns are commonly derived from verbs with the help of the agent suffix -er.
Closely connected with Historical Lexicology is Contrastive and Comparative Lexicology whose aims are to study the correlation between the vocabularies of two or more languages, and find out the correspondences between the vocabulary units of the languages under comparison.

The word is in the centre of investigation.

Word is a central unit of speech, it is a smallest autonomous (it can move around in the sentence more or less) meaningful unit of L. It is a 2faced unit (form+meaning). A morpheme is also a 2facet, meaningful unit, but not autonomous.
What can be studied about a word?
The branches of L.

1. 
   semantics, semasiology (studies meanings)
   

Problems: the definition of meaning, types of meaning, motivation, changes in the meaning, polysemy, homonymy, lexico-semantic groups of ws, synonyms, antonyms, methods of semantic analysis.

2. 
   morphology and word-formation (the structure of words, ways of word-building)
   

Problems: the segmentation of words into morphemes, the classification of morphemes, means of word-building, their productivity)
Ex. Walker, a walk, walkabout, walk way

3. 
   etymology (the origin and evolution of words and their meanings)
   

Problems: native words and borrowings, assimilation, its types and degrees, ways of enriching word stock)
Ex. Phenomenon, polka, tycoon, sauna

4. 
   Phraseology (word combinations and phraseological units (PhUs)
   

Problems: valency and collocability, the structure of PhUs, transference of meaning, types of PhUs.
Ex. Pressing, heavy question, by the way, bread and cheese marriage (брак с бедняком)

5. 
   Dialectology (variants and dialects of E.)
   

Problems: general characteristics, lexical differences, how dialects were forming, their relationship with standard E., British and American dialects, standard E.
Ex. Flat – apartment
Mad-crazy
Biscuit-cookie

6. 
   Lexicography (compilations of dictionaries)
   

Problems: types of dics, the principles of word selection, ways of building the entry, ways of defining the word’s meaning(s), dic structure.
Ex. Encyclopedic dics, Linguistic Dics.

7.