Prof. Haiping Long, Sun Yat-Sen University, China:
Old Chinese shì was polysemous because it underwent poly-grammaticalization: it followed one hypothetical pathway (i.e., pronominal demonstrative > manner demonstrative > manner demonstrative verb > affirmative adjective) to have developed into an affirmative adjective, and followed the other hypothetical pathway (i.e., pronominal demonstrative > copula) to have developed into a copula. Its usages as a pronominal demonstrative, a manner demonstrative, and a manner demonstrative verb almost all disappeared in Middle Chinese.
Speakers of languages (dialects) in contact with Chinese adopted one of the three strategies to introduce the polysemy into their languages (dialects): (a) to use the loanwords of Chinese shì to function as copulas and affirmative adjectives, (b) to use copulas of the target languages to function as affirmative adjectives, (c) to use adjectives meaning ‘true, correct’ of the target languages to function as copulas. The three strategies help to explain the formation of copula-adjective polysemy in these languages (dialects). This talk also summarizes possible grammaticalizational pathways of shì structures in Chinese.