Determiners are words like the, an, my, some. They are grammatically similar. They all come at the beginning of noun phrases, and usually we cannot use more than one determiner in the same noun phrase.
Articles:a, an, the
Possessive Adjectives:my, your, his, her, its, our, their, whose
less, leastfew, fewer, fewestwhat, whatever; which, whicheverboth, half,
Either and neither are used in sentences concerning a possible choice between two items.Either can mean one or the other (of two) or each of two.
For example:-I've got tea and coffee, so you can have either.
(One or the other)The room has a door at either end.
(Both)Neither means not the first one and not the second one.
For example:-Neither of the students were listening.