Phonetics (from the Greek word φωνή, phone = sound/voice) is the study of sounds (voice). It is concerned with the actual properties of speech sounds (phones) as well as those of non-speech sounds, and their production, audition and perception, as opposed to phonology, which operates at the level of sound systems and abstract sound units (such as phonemes and distinctive features). Phonetics deals with the sounds themselves rather than the contexts in which they are used in languages. Discussions of meaning (semantics) therefore do not enter at this level of linguistic analysis.
While writing systems and alphabets are in many cases closely related to the sounds of speech, strictly speaking, phoneticians are more concerned with the sounds of speech than the symbols used to represent them. So close is the relationship between them however, that many dictionaries list the study of the symbols (more accurately semiotics) as a part of phonetic studies. On the other hand, logographic writing systems typically give much less phonetic information, but the information is not necessarily non-existent. For instance, in Chinese characters, a phonetic refers to the portion of the character that hints at its pronunciation, while the radical refers to the portion that serves as a semantic hint. Characters featuring the same phonetic typically have similar pronunciations, but by no means are the pronunciations predictably determined by the phonetic due to the fact that pronunciations diverged over many centuries while the characters remained the same. Not all Chinese characters are radical-phonetic compounds, but a good majority of them are.
Phonetics has three main branches:
1. Articulatory phonetics, concerned with the positions and movements of the lips, tongue, vocal tract...