Either, neither, and both are used when talking about two things or people. They have distinct meanings and grammatical patterns. Getting them right signals a confident intermediate level of English.
3 subtopics — pick one to start practising
Both — The Two Together
Use both when you mean "the two" together in a positive way. Both can be a determiner before a plural noun (both students), a pronoun replacing a noun (both are correct), or part of a correlative conjunction (both… and…). Both always refers to exactly two things.
Either — One or the Other
Use either to mean "one or the other (but not both)" when giving a choice between two options. As a determiner it takes a singular noun and singular verb: "Either option is fine." In the correlative "either… or…", the verb agrees with the noun closest to it.
Neither — Not One and Not the Other
Use neither to mean "not one and not the other" — a negative statement about two things. As a determiner it takes a singular noun and singular verb: "Neither option is perfect." In "neither… nor…", the verb agrees with the closer noun. Never add "not" alongside neither — it already carries the negative meaning.