Processes underlying the development of pragmatic markers

English(I) sayexhibits a variety of uses as a conjunction (meaning ‘suppose’), an adverb (meaning ‘about’ or ‘for example’), and a pragmatic marker (preceding questions, expressing surprise, evoking the hearer's attention, clarifying, or emphasising). Using the historical development of these forms as a test case of grammaticalisation, pragmaticalisation, lexicalisation, or idiomaticisation, this paper argues that despite being seen as ‘mirror images’, grammaticalisation and lexicalisation may be complementary processes, involving an increase in semantic opacity and the erasure of phrasal or morphological boundaries. However, the development of(I) sayis best understood as grammaticalisation as it involves decategorialisation from major to minor word class, the shift from referential to non-referential meaning, and the coding of invited inferences, all of which are typical of grammaticalisation.