Acceptability judgments are reports of a speaker’s or signer’s subjective sense of the well-formedness, nativeness, or naturalness of (novel) linguistic forms. Their value comes in providing data about the nature of the human capacity to generalize beyond linguistic forms previously encountered in language comprehension. For this reason, acceptability judgments are often also called grammaticality judgments (particularly in syntax), although unlike the theory-dependent notion of grammaticality, acceptability is accessible to consciousness. While acceptability judgments have been used to test grammatical claims since ancient times, they became particularly prominent with the birth of generative syntax. Today they are also widely used in other linguistic schools (e.g., cognitive linguistics) and other linguistic domains (pragmatics, semantics, morphology, and phonology), and have been applied in a typologically diverse range of languages. As psychological responses to linguistic stimuli, acceptability judgments are experimental data. Their value thus depends on the validity of the experimental procedures, which, in their traditional version (where theoreticians elicit judgments from themselves or a few colleagues), have been criticized as overly informal and biased. Traditional responses to such criticisms have been supplemented in recent years by laboratory experiments that use formal psycholinguistic methods to collect and quantify judgments from nonlinguists under controlled conditions. Such formal experiments have played an increasingly influential role in theoretical linguistics, being used to justify subtle judgment claims or new grammatical models that incorporate gradience or lexical influences. They have also been used to probe the cognitive processes giving rise to the sense of acceptability itself, the central finding being that acceptability reflects processing ease. Exploring what this finding means will require not only further empirical work on the acceptability judgment process, but also theoretical work on the nature of grammar.
Number is the category through which languages express information about the individuality, numerosity, and part structure of what we speak about. As a linguistic category it has a morphological, a morphosyntactic, and a semantic dimension, which are variously interrelated across language systems. Number marking can apply to a more or less restricted part of the lexicon of a language, being most likely on personal pronouns and human/animate nouns, and least on inanimate nouns. In the core contrast, number allows languages to refer to ‘many’ through the description of ‘one’; the sets referred to consist of tokens of the same type, but also of similar types, or of elements pragmatically associated with one named individual. In other cases, number opposes a reading of ‘one’ to a reading as ‘not one,’ which includes masses; when the ‘one’ reading is morphologically derived from the ‘not one,’ it is called a singulative. It is rare for a language to have no linguistic number at all, since a ‘one–many’ opposition is typically implied at least in pronouns, where the category of person discriminates the speaker as ‘one.’ Beyond pronouns, number is typically a property of nouns and/or determiners, although it can appear on other word classes by agreement. Verbs can also express part-structural properties of events, but this ‘verbal number’ is not isomorphic to nominal number marking. Many languages allow a variable proportion of their nominals to appear in a ‘general’ form, which expresses no number information. The main values of number-marked elements are singular and plural; dual and a much rarer trial also exist. Many languages also distinguish forms interpreted as paucals or as greater plurals, respectively, for small and usually cohesive groups and for generically large ones. A broad range of exponence patterns can express these contrasts, depending on the morphological profile of a language, from word inflections to freestanding or clitic forms; certain choices of classifiers also express readings that can be described as ‘plural,’ at least in certain interpretations. Classifiers can co-occur with other plurality markers, but not when these are obligatory as expressions of an inflectional paradigm, although this is debated, partly because the notion of classifier itself subsumes distinct phenomena. Many languages, especially those with classifiers, encode number not as an inflectional category, but through word-formation operations that express readings associated with plurality, including large size. Current research on number concerns all its morphological, morphosyntactic, and semantic dimensions, in particular the interrelations of them as part of the study of natural language typology and of the formal analysis of nominal phrases. The grammatical and semantic function of number and plurality are particularly prominent in formal semantics and in syntactic theory.