Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
plus (adv., adj., n., prep., coord. conj.)
As preposition and conjunction, plus is Standard in some uses. One plus one equals two illustrates the Standard mathematical use meaning “and”; note that it ordinarily doesn’t change the verb to plural as and would, which suggests that in this use plus is a preposition. Nor does the preposition plus make the verb plural in nonmathematical use: The wind, plus several inches of rain, has caused many power outages. But plus can also be a conjunction, and this shows when the verb shifts to plural: The growing unemployment plus [and] the oil price increase have unsettled the stock market. This use is also Standard. The conjunctive plus is limited mainly to Conversational and Informal uses, such as I don’t have time to go with you, plus I don’t have any money either. Uses of plus as a sentence adverb meaning “besides” also seem to be Conversational and Informal only: She hates having to wait around. Plus it’s raining. As an adjective, as in That she’s got her own car is a plus factor, and noun, as in The short commute to my job is a plus for me, plus is Conversational and perhaps Semiformal; it seems not to appear much in Formal writing, but it does occur in some Edited English.
