phoneme, phonemic: A phoneme is a sound which contrasts with other sounds of a language. Distinctions between phonemes (that is, distinctions which cause contrast) are called phonemic distinctions.

Two sounds which are pronounced differently are phonetically different, but if that difference does not produce contrast it is not phonemic but rather allophonic. For instance in English the p sound of "pit" [phIt] is phonetically different from the p sound of "spit" [spIt], because it has a puff of air after the lips open (represented in transcription by the superscript h). But that difference is not phonemic, because all p's following initial s in English are pronounced that way; the phonemic contrast is carried by the presence vs. absence of the s and the p varies its pronunciation according to its context. Thus, we say that there is just one phoneme /p/, which has two allophones, [ph] and [p]. (Phonemes are sometimes written between slashes [4].)

Minimal pairs are especially important for establishing that a distinction is phonemic. Generally each phoneme should be represented in a practical orthography by a different grapheme (e.g., a letter of the alphabet), but the differences between allophones should not be represented. [Spanish: fonema, fonémico]