lexicology
Lexicology (noun) means the branch of linguistics concerned with words: their nature and meaning, the parts they are made of, the relations between words including relations of meaning, groups of words, and the lexicon as a whole.
Etymology
From Ancient Greek λεξικός (lexikós, "of words"), from λέξις (léxis, "a saying, speech, word"), from λέγειν (légein, "to speak"); analysed on the surface, it is lexico- + -logy.