A branch of linguistics which studies the systematic organisation of speech sounds. It has traditionally focused largely on study of the systems of phonemes in particular languages, but it may also cover any linguistic analysis either at a level beneath the word (including syllable, onset and rhyme, articulatory gestures, articulatory features, mora, etc.) or at all levels of language where sound is considered to be structured for conveying linguistic meaning. Phonology also includes the study of equivalent organisational systems in sign languages.