Both ... and is a paired conjunctions. Paired conjunctions are used to express actions that two or more subjects take. Other paired conjunctions include 'either ... or' and 'neither ... nor'. As 'both ... and' refers to two subjects the plural form of the verb is always used. However, 'either ... or' and 'neither ... or' can take the singular and the plural form of the verb.
Both … and
Subjects connected by 'both … and' take the a plural conjugation.
Both Alice and Janice attended USC.
Both Jim and Peter are attending the conference in New York this weekend.
Either … or
'Either … or' is used in sentences in a positive sense meaning "one or the other, this or that, he or she, etc." Verb conjugation depends on the subject (singular or plural) closest to the conjugated verb.
Either Peter or the girls need to attend the course. (second subject plural)
Either Jane or Matt is going to visit next weekend. (second subject singular)
Neither … nor
'Neither … nor' is used in sentences in a negative sense meaning "not this one nor the other, not this nor that, not he nor she, etc.". Verb conjugation depends on the subject (singular or plural) closest to the conjugated verb.
Neither Frank nor Lilly lives in Eugene. (second subject singular)
Neither Axel nor my other friends care about their future. (second subject plural)
Do you understand the rules? Test your knowledge with this both ... and, neither ... nor, either ... or quiz.