In some models ofphonology as well asmorphophonology in the field oflinguistics, theunderlying representation (UR) orunderlying form (UF) of aword ormorpheme is the abstract form that a word ormorpheme is postulated to have before anyphonological rules have been applied to it.[1][2] In contrast, asurface representation is thephonetic representation of the word or sound. The concept of an underlying representation is central togenerative grammar.[3]
If more phonological rules apply to the same underlying form, they can apply wholly independently of each other or in afeeding orcounterbleeding order. The underlying representation of a morpheme is considered to be invariable across related forms (except in cases ofsuppletion), despitealternations among variousallophones on the surface.
In many cases, the underlying form is simply thephonemic form. For example, in many varieties ofAmerican English, the phoneme/t/ in a word likewet can surface either as anunreleased stop[t̚] or as aflap[ɾ], depending on environment:[wɛt]wet vs.[ˈwɛɾɚ]wetter. (In both cases, however, the underlying representation of the morphemewet is the same: its phonemic form/wɛt/.)
Phonological rules may change the phonemes involved. In such cases, pipes ("|") or double slashes may be used in transcription to distinguish the underlying form from its phonemic realization. For example, the word "cats" has the phonemic representation/kæts/. If it is assumed that the underlying form of the English plural suffix is a[z] sound, the underlying form of "cats" would be//kætz//. (The[z] surfaces as an[s] because of the phonological process of devoicing after an unvoiced consonant.)
Sandhi, such astone sandhi inChinese, is another phonological process that changes the phonemes of a morpheme from its underlying form.
