FREQUENCY OF OCCURRENCE. The number of times or the regularity with which something happens. Linguists and language teachers often take account of the frequency of occurrence of linguistic items and features. Geographic, socioeconomic, and ethnic varieties of a language generally differ in the frequency with which choices are made rather than in the presence or absence of an item or feature: for example, the use of negative too in spoken WELSH ENGLISH, as in She won't do it, too (as opposed to either). The same applies to stylistic variation in spoken and written language (ELLIPSIS and CONTRACTION are, for example, more frequent in SPEECH), such REGISTERS as legal language (which makes frequent use of compounds such as hereinafter and thereof), and religious language (with its use of thou-pronouns and corresponding verb forms), and in contrasts along the continuum from the most formal to the most casual (the choice of furthermore and moreover as opposed to also and too).

Language change commonly arises from the dominance of one variable over others and can often be observed through FREQUENCY COUNTS. The characteristics of a genre, author, or work may be identified through the relative frequency of items of VOCABULARY or of GRAMMAR features; this has been used to identify the disputed authorship of works and disputed passages in statements to the police. Information about frequency is commonly taken into account in selecting entries for dictionaries and ordering definitions within entries, as well as in grading material for learners of a language. Sociolinguists usually draw their evidence for relative frequencies from analyses of observed or elicited speech, sometimes incorporating the results in statements of probability. Some linguists have collected large corpora of written or spoken samples of a language, their frequency lists and studies of data made easier by computational processing. Recent experiments have obtained evidence of the perception of relative frequencies by eliciting judgements from native speakers: for example, of the relative frequencies of the subjunctive (We urge that he give his reasons), the should-construction (We urge that he should give his reasons), and the indicative (We urge that he gives his reasons). See CORPUS, VOCABULARY CONTROL.