In contrast, morphological typology is the classification of languages according to their "use" of morphemes, while lexicology is the study of those words forming a language's wordstock.
en.wikipedia.org It is in fact most commonly understood as a branch of lexicology, the study of words (although some apply the term also to grammar and conversation).
en.wikipedia.org Contrastive descriptions can occur at every level of linguistic structure: speech sounds (phonology), written symbols (graphology), word-formation (morphology), word meaning (lexicology), collocation (phraseology), sentence structure (syntax) and complete discourse (textology).
en.wikipedia.org Lexicology collects words and their derivations and transformations: it has not given rise to much generalized theory.
en.wikipedia.org When "al" - occurs in places where we would not normally expect it, it is considered extra as far as grammar and lexicology are concerned.
en.wikipedia.org