The Editor’s Manual
Free learning resource on English grammar, punctuation, usage, and style.
When the words in a compound subject are joined by “and,” it is plural. When they are joined by “or” or “nor,” the verb should agree with the part closest to it. When phrases like “as well as” are attached to a singular subject, it stays singular.
Use there is or there’s when the noun that follows is singular (“There is a dog”) and there are when the noun is plural (“There are two dogs”). There’s is sometimes also used with a plural noun in speech and informal writing (“There’s a dog and a cat on the rug”).
Collective nouns such as “team” are treated as singular in American but plural in British English. It also depends on whether you want to refer to the group as a whole or to the individual members of the group.
Data can be a plural noun (“the data are”) or a singular mass noun (“the data is”). As a mass noun, it is used much like the word “information.”