Lexical morphemes and grammatical morphemes
It is a common observation that grammatical morphemes often develop gradually from lexical morphemes. Some languages show this fact more transparently than others. For example, Sebba (1997) observes that creoles and pidgins often use lexically contentful elements with the meaning of ‘finish’ or ‘done’ as functional markers signaling that the event described by the sentence occurs before the time of utterance:
(1) mo fin mahze (Mauritian Creole)
I finish eat
(2) me waka kba (Sranan Tongo)
I walk finished
‘I had walked.’
(3) mipela I ting olsem i mas dai pinis (Tok Pisin)
we him think anyhow him must die finish
‘We think he must have died.’
(4) a don kom (Pidgin of West Africa)
I done come
‘I have come.’
Similar examples from other spoken languages are offered by Pfau and Steinbach (2006). In Rama (a spoken language of Nigeria), the verb aktul meaning ‘finish’ is now used as a completive marker, and in Lhasa (spoken in Tibet), the verb tshaa meaning ‘finish’ marks perfective aspect.
Examples of this sort are also quite common in sign languages. For instance, the signs FINISH and FATTO belonging, respectively, to American Sign Language (ASL) and Italian Sign Language (LIS), can both occur as lexically contentful main verbs with the meaning of ‘finish’ (or ‘done’) and as aspectual/temporal morphemes. Both signs, when acting as grammatical morphemes, also exhibit a peculiar behavior with negation and negative quantifiers.