English — both / either / neither
These three words all refer to a pair of two things. Both means the two together, either means one or the other, and neither means not one and not the other: both books, either book, neither book.
How it works
Both takes a plural verb (Both windows are open). Either and neither take a singular verb (Either window is fine; Neither answer is correct). With the pair words use either...or for choice (either tea or coffee) and neither...nor for exclusion (neither tea nor coffee). Before a noun say both, either or neither directly; before a pronoun or the, add of: both of us, either of them, neither of these.
Examples
| Example | Meaning / pattern |
|---|---|
| Both books are new. | the two together — plural verb (are) |
| Both of us agree. | both + of before a pronoun |
| Either day is fine. | one of the two — singular verb (is) |
| You can have either tea or coffee. | choice between two: either...or |
| Neither answer is correct. | not one of the two — singular verb (is) |
| Neither Tom nor Anna came. | excluding both: neither...nor |
| Neither of them was ready. | neither + of + pronoun, usually singular verb |
Good to know
All three refer to exactly two items — for three or more use all, any or none. Neither is already negative, so don't add another negative: say Neither of them came, not Neither of them didn't come. In careful writing either/neither take a singular verb, but in speech Neither of them were ready is common. When either...or or neither...nor join two subjects, the verb usually agrees with the nearer one: Neither the students nor the teacher was late.