Not one or the other; not either: Neither shoe feels comfortable.
Not either one; not the one or the other: Neither of the twins is here. Neither will do. Neither of them is incorrect.
Not either; not in either case. Used with the correlative conjunction nor: Neither we nor they want it. She neither called nor wrote. I got neither the gift nor the card.
Also not: If he won't go, neither will she.
Similarly not; also not: Just as you would not, so neither would they.