What is the meaning of Phonology?

The study of the way sounds function in languages, including accent, intonation, phonemes, stress, and syllable structure, and which sounds are distinctive units within a language; the way sounds function within a given language; a phonological system.

The study of the way components of signs function in a sign language, and which components are distinctive units within the language; the way components of signs function within a given sign language.

Source: wiktionary.org