The semantic and grammatical overlap of as and that

Literature on British dialects (overview in Kortmann 2005: 1095) has already widely reported the use of the as-relativizer. However, as also occurs as complementizer in non-standard English. This paper explores how the lexis-grammar interface enables one lexeme – as – to become a non-standard grammatical variant of another lexeme – that – in two grammatical functions. The fact that as and that are of demonstrative origin enables the use of both items in anaphoric and cataphoric contexts. Whilst diachronic corpus data support the grammaticalization of that and of the as-relativizer as described in the Oxford English Dictionary, the grammaticalization of the complementizer as remains unclear. This paper offers an alternative path of grammaticalization based on observations in synchronic corpus data and parallels in as-constructions.