In the representation of syntagmatic relations in language, we may distinguish between a linear sequence of classes, such as ‘adjective followed by noun’, and a non-linear configuration of functions, such as ‘modifier-head relation’ or simply ‘modification’. Both of these have been referred to as ‘structure’, although this term has also been extended to cover paradigmatic as well as syntagmatic relations. For Hjelmslev, for whom ‘structure’ was not a technical term (see e.g. 1961: 74 (=1943: 67)), ‘the structural approach to language … [is] conceived as a purely relational approach to the language pattern’ (1948: quoted in Firth, 1951: 220); among others who have emphasized the relational aspect of such studies are Firth (1957: 17 ff., 1951: 227–8; cf. Robins, 1953; Palmer, 1964a), Tesnière (cf. Robins, 1961: 81 ff.) and Pike(cf. Longacre, 1964: 16). Chomsky's (1964: 32) distinction, using Hockett's terms, between ‘surface structure’ and ‘deep structure’, ‘structure’ here going beyond syntagmatic relations, is extremely valuable and widely accepted: the surface structure of a sentence is defined as ‘a proper bracketing of the linear, temporally given sequence of elements, with the paired brackets labelled by category names’, while the deep structure, which is ‘in general not identical with its surface structure’, is ‘a much more abstract representation of grammatical relations and syntactic organization’.