Phoneme
What Is Phoneme?
In linguistic, languagesOpens in new window are organized hierarchically, thus, sentences are formed from phrases; phrasesOpens in new window from words; wordsOpens in new window from syllables; and syllables from phonemes.
Phoneme refers to the smallest segmental unit of speech that distinguishes meaningful words.
For example, in English language, the words light and right are pronounced differently only on the initial consonants /l/ and /r/. Therefore, /l/ and /r/, are different phonemes in the English language.
A phoneme may have more than one variant, called an allophoneOpens in new window, which functions as a single sound; for example, the p’s of “pat,” “spat,” and “tap” differ slightly phonetically, but that difference, determined by context, has no significance in English.
It is widely observed that phonemes are language specific. Most languages have a huge number of phonemes that ranges from twenty to sixty. In some languages, where the variant sounds of p can alter meaning, they are classified as separate phonemes, for example, in Thai the aspirated p (pronounced with an accompanying puff of air) and unaspirated p are distinguished one from the other.

Although the pronunciation of a phoneme can be slightly different in various contexts, a phoneme has relatively stable articulatory and acoustic properties.