Underlying representation


In some models of phonology as well as morphophonology in the field of linguistics, the underlying representation or underlying form of a word or morpheme is the abstract form that a word or morpheme is postulated to have before any phonological rules have applied to it. By contrast, a surface representation is the phonetic representation of the word or sound. The concept of an underlying representation is central to generative grammar.
If more phonological rules apply to the same underlying form, they can apply wholly independently of each other or in a feeding or counterbleeding order. The underlying representation of a morpheme is considered to be invariable across related forms, despite alternations among various allophones on the surface.

Examples

In many cases, the underlying form is simply the phonemic form. For example, in many varieties of American English, the phoneme in a word like wet can surface either as an unreleased stop or as a flap, depending on environment: wet vs. wetter.
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. If it is assumed that the underlying form of the English plural suffix is a sound, the underlying form of "cats" would be.
Sandhi, such as tone sandhi in Chinese, is another phonological process that changes the phonemes of a morpheme from its underlying form.