levelling (n.)

In HISTORICAL LINGUISTICS, the gradual loss of a linguistic distinction, so that forms which were originally CONTRASTIVE become identical. For example, Old English nouns generally distinguished NOMINATIVE and ACCUSATIVE cases, but in Modern English these have been levelled to a single form. The term is also used in DIALECTOLOGY, where it refers to the lessening of differences between regional dialects as a result of social forces (such as the media) which are influencing people to speak in a similar way. The spread of the phenomenon of (certain features of) ESTUARY ENGLISH throughout England in the later decades of the twentieth century is an illustration. In PHONETICS, analogical levelling is the extension of a phonetic property from one member of a PARADIGM to another in contexts that are not otherwise predicted by the PHONOLOGICAL RULES of a language; for example, [e] replaced by  in condensation on analogy with condense