Phonology is a branch of linguistics that studies how languages or dialects systematically organize their sounds (or constituent parts of signs, in sign languages). The term also refers to the sound or sign system of any particular language variety. At one time, the study of phonology only related to the study of the systems of phonemes in spoken languages. Now it may relate to(a) any linguistic analysis either at a level beneath the word (including syllable, onset and rime, articulatory gestures, articulatory features, mora, etc.), or(b) all levels of language where sound or signs are structured to convey linguistic meaning.[1]
Sign languages have a phonological system equivalent to the system of sounds in spoken languages. The building blocks of signs are specifications for movement, location and handshape.[2]