Both of these provide a problem because in neither case is it immediately clear whether the subject is singular or plural. With a little help from our friends in Star Trek -
With "none of them" the question is, which of the two words, 'none' or 'them' is the actual subject of the sentence. The temptation is to assume that the word immediately before the verb is the subject, but -
'None' is a group or collective word and these are normally treated as one item; the 'of...' is what the group consists of, in this case 'them', although we don't know how many of 'them' there are. Therefore the actual subject of the sentence is 'none'.
"Those are my officers. I know them well. None of them is a traitor," Kirk snapped.Add to that, 'them' is objective case; the subjective plural pronoun is 'they'. You would never, for example, say 'Them are walking down the road.'
Group words include ones like audience, committee, family, gang, orchestra, team, herd, flock, pair, bunch, crew - all of those take a singular verb.
"It's been an arduous mission, Captain. The crew is needing shore leave," McCoy told Kirk.In addition, 'none' means 'not one', and the 'one' is the absolute giveaway - it takes a singular verb, ie 'is'.
Occasionally, however, there's an exception to this; where you have a group word where treating it as one entity is clumsy - because 'crew' is a group word, grammatically it should be
The Enterprise crew was at its stationbut that doesn't make sense; although it's one crew, everyone in it has a different station, so it's more logical to say
The Enterprise crew were at their stationswhere the meaning is 'the (members of the) Enterprise crew...' In a case like this, you either use the plural verb or, better, add 'members of', so that 'members' becomes the subject of the sentence.
With "neither" we're talking about one of only two items, therefore it, too, is singular.
Neither Spock nor McCoy was prepared to admit that he was wrong.Related to 'neither' is 'either', which again refers to one of two -
Kirk shook his head, frustrated. Either Spock or McCoy was right, each of them believed he was, and Kirk found it impossible to decide between them.If you remember that you are referring to one group (no matter how big it is) or one person it should be easy to remember that the verb to use is normally 'is' (or 'was').
Learn English here
The Free Dictionary here, here and