Phonetic environment

In phonetics and linguistics, the phonetic environment of a given instance of a speech sound (or "phone") consists of the other phones adjacent to and surrounding it. The phonetic environment of a phone can sometimes determine the allophonic or phonemic qualities of a sound in a given language.

For example, the English vowel 'a' /æ/ in the word 'mat' /mæt/ has the consonants /m/ preceding it and /t/ following it. In linguistic notation it is written as /m_t, where the slash can be read as "in the environment", and the underscore represents the target phone's position relative to its neighbours. The expression therefore can be read as "in the environment after m and before t".