Halliday & Matthiessen (2014: 607-8):
…the different types of cohesion make distinct contributions to the creation and interpretation of text, contributions that complement one another. This complementarity can be described in terms of two distinctions, (i) one having to do with the extent of the elements that are linked cohesively and (ii) the other with the location of cohesive resources within lexicogrammar.
(i) We can make a distinction between CONJUNCTION and the three other resources of cohesion. As we have seen, conjunction is concerned with rhetorical transitions — transitions between whole ‘messages’, or even message complexes. Conjunction indicates the relations through which such textual transitions are created. In contrast, the other cohesive resources are concerned with textual statuses — statuses having to do with how ‘components’ of messages are processed as information …
(ii) At the same time, we can also recognise that the systems of cohesion operate within either the grammatical zone or the lexical zone of the lexicogrammatical continuum. CONJUNCTION, REFERENCE and ELLIPSIS are all grammatical systems, and are thus all manifestations of what we might call grammatical cohesion. The point of origin of each of these systems falls within one or more particular grammatical unit; and terms within these systems are realised either by grammatical items that have some particular place within the structure of that unit or (in the case of ellipsis) by the absence of elements of grammatical structure. … In contrast, LEXICAL COHESION operates within the lexical zone of the lexicogrammatical continuum; and it follows the general principle that lexical items are not defined in terms of particular grammatical environments.
Table 9-5 shows how (i) and (ii) intersect to define the overall space of cohesive systems in English.
