ambiguity a phonological (or orthographic) form having multiple meanings (senses, characters, semantic representations) assigned by the language system. A lexical ambiguity occurs when a lexical item (word) is assigned multiple meanings by the language. It includes (a) homonymy, i.e., distinct lexical items having the same sound or form but different senses – ‘knight’/’night’, ‘lead’ (n.)/’lead’ (v.), ‘bear’ (n.)/’bear’ (v.); and (b) polysemy, i.e., a single lexical item having multiple senses – ‘lamb’ (the animal)/’lamb’ (the flesh), ‘window’ (glass)/’window’ (opening). The distinction between homonymy and polysemy is problematic.
A structural ambiguity occurs when a phrase or sentence is correlated by the grammar of the language with distinct constituent structures (phrase markers or sequences of phrase markers). Example: ‘Competent women and men should apply’ – ‘[NP[NPCompetent women] and men] . . .’ vs. ‘[NPCompetent[NPwomen and men]] . . .’, where ‘NP’ stands for ‘noun phrase’. A scope ambiguity is a structural ambiguity deriving from alternative interpretations of scopes of operators (see below). Examples: ‘Walt will diet and exercise only if his doctor approves’ – sentence operator scope: doctor’s approval is a necessary condition for both diet and exercise (wide scope ‘only if’) vs. approval necessary for exercise but not for dieting (wide scope ‘and’); ‘Bertie has a theory about every occurrence’ – quantifier scope: one grand theory explaining all occurrences (‘a theory’ having wide scope over ‘every occurrence’) vs. all occurrences explained by several theories together (‘every occurrence’ having wide scope). The scope of an operator is the shortest full subformula to which the operator is attached. Thus, in `(A & B) C’, the scope of ‘&’ is ‘(A & B)’. For natural languages, the scope of an operator is what it C-commands. (X C-commands Y in a tree diagram provided the first branching node that dominates X also dominates Y.) An occurrence of an operator has wide scope relative to that of another operator provided the scope of the former properly includes scope of the latter. Examples: in ‘~(A & B)’, ‘-‘ has wide scope over ‘&’; in ‘(Dx) (Ey) Fxy’, the existential quantifier has wide scope over the universal quantifier. A pragmatic ambiguity is duality of use resting on pragmatic principles such as those which underlie reference and conversational implicature; e.g., depending on contextual variables, ‘I don’t know that he’s right’ can express doubt or merely the denial of genuine knowledge. See also IMPLICATURE, MEANING, PHILOSO- PHY OF LANGUAGE , PRAGMATIC CONTRADIC — TION , SCOPE , VAGUENES. W.K.W.