We begin our study of language by examining the inventory, structure and functions of the speech sounds. This branch of linguistics is called phonetics.
Phonetics is an independent branch of linguistics like lexicology or grammar. These linguistic sciences study language from three different points of view. Lexicology deals with the vocabulary of language, with the origin and development of words, with their meaning and word building. Grammar defines the rules governing the modification of words and the combination of words into sentences. Phonetics studies the outer form of language; its sound matter. The phonetician investigates the phonemes and their allophones, the syllabic structure the distribution of stress, and intonation. He is interested in the sounds that are produced by the human speech-organs insofar as these sounds have a role in language. Let us refer to this limited range of sounds asthe phonic medium and to individual sounds within that range as speech-sounds. We may now define phonetics as the study of the phonic medium. Phonetics is the study of the way humans make, transmit, and receive speech sounds. Phonetics occupies itself with the study of the ways in which the sounds are organized into a system of units and the variation of the units in all types and styles of spoken language.
Phonetics is a basic branch of linguistics. Neither linguistic theory nor linguistic practice can do without phonetics. No kind of linguistic study can be made without constant consideration of the material on the expression level.