fonem

In linguistics, a fonem (phoneme) is the smallest unit of sound in a language that can distinguish meaning. It is an abstract mental category that underlies a set of physically realized speech sounds called phones; these phones are considered variants of the same phoneme in a given language. A phoneme contrasts with other phonemes to create differences in word meaning. For example, in English the sounds /p/ and /b/ distinguish pat and bat, forming distinct phonemes in that language.

Within a language, a phoneme can appear in different phonetic realizations called allophones, which are predictable from context. These allophones do not change meaning, so they are not separate phonemes. An everyday illustration is the /p/ in "pat" (aspirated [pʰ]) versus the /p/ in "spin" (unaspirated [p]), where the variation depends on surrounding sounds.

Phonology is the study of how phonemes are organized and interact, including the inventory of a language’s phonemes, phonotactics (allowed sound sequences), and processes that alter sounds (such as assimilation or nasalization). The relationship between phonemes and spelling is not always direct; writing systems may reflect historical or morphological factors rather than a one-to-one phoneme representation.

Historically, the concept of phonemes emerged in 19th- and 20th-century linguistics and is central to modern phonology. Phonemes are language-specific; the same set of sounds can be grouped into different phoneme inventories across languages. Understanding phonemes helps explain why speakers perceive certain sound contrasts as meaningful within their language.