Underlying representation
（重定向自Underlyingly）
In some models of phonology as well as morphophonology in the field of linguistics, the underlying representation (UR) or underlying form (UF) 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.