iso-

A PREFIX used in DIALECTOLOGY as part of the labelling of the various types of LINGUISTIC information which can be displayed on maps (‘linguistic atlases’). The most widely used notion is that of the isogloss (or isograph, or isoglottic line), a line drawn on a map to mark the boundary of an area in which a particular linguistic feature is used. A number (or ‘bundle’) of isoglosses falling together in one place suggests the existence of a dialect boundary. Further distinctions can be made in terms of the kind of linguistic feature being isolated: an isophone is a line drawn to mark the limits of a PHONOLOGICAL feature: an isomorph marks the limits of a MORPHOLOGICAL feature; an isolex marks the limits of a LEXICAL ITEM; an isoseme marks the limits of a SEMANTIC feature (as when lexical items of the same phonological form take on different MEANINGS in different areas). Other distinctions have been suggested, based on the same principle. An alternative terminology talks of isophonic/isomorphic/ . . . ‘lines’.

An isopleth is a more general notion, being used by some SOCIOLINGUISTS to refer to a line which marks the limits of a linguistic feature seen in association with relevant sociocultural features. An isolect is a term used by some sociolinguists to refer to a linguistic VARIETY (or LECT) which differs minimally from another variety (i.e. a single isogloss, whether of a regional or a social kind, differentiates them).