Phonetics is the systematic study of the human ability to make and hear sounds which use the vocal organs of speech, especially for producing oral language. It is usually divided into the three branches of (1) articulatory, (2) acoustic and (3) auditory phonetics. It is also traditionally differentiated from the field of phonology, which is the formal study of the sound systems (phonologies) of languages, especially the universal properties displayed in ALL languages, such as the psycholinguistic aspects of phonological processing and acquisition.