pro- nouns/verbs/adjective/adverbs

Besides pronouns, English also contains pro-verbs, such as the ‘did’ in ‘Mary ran quickly, so Bill did too’, and pro-adjectives such as ‘such’ in ‘The happy man was no longer such’; and pro-adverbs such as the ‘so’ in ‘She twitched violently and, while so twitching, expired’.

KIRKHAM, RICHARD L. (1998). Truth, deflationary theories of. In E. Craig (Ed.), Routledge Encyclopedia of Philosophy. London: Routledge. Retrieved September 07, 2007, from http://www.rep.routledge.com/article/N062SECT2