Funny things, plurals. Two weeks ago, I was lamenting the way a few are misused as singular nouns. But a host of singular nouns are used as plural ones. What about them? Shouldn’t that sentence read A host...is used...?

No: indeed that particular example would be absurd with is for are. But usually there’s a choice. A host of proposals await/awaits decision in Delhi; either version is fine. Ditto with other nouns used as a way of saying many: an army of cockroaches has/have invaded my kitchen; a plethora of daft ideas is/are in the air. Journalists would add a raft of and a slew of (but not a lot of: it always needs a plural verb).

Which version is better? There’s no firm guide. But the sense may suggest your choice: a series of brutal murders have shocked Mumbai would be better with has shocked if you want to emphasize that it was indeed a connected series, not just a random collection. Likewise, collective nouns almost always offer a choice. The crowd are angry, the audience is impatient, the orchestra are on strike, the cabinet are a bunch of clowns. There is no firm guide, but sense may help: the family has emigrated to America, the team are all grossly overpaid.

With team we meet the linguistic niceties of sport. In British and Indian usage, teams are plural: England beat India, (OK, just joking), Oxford beat Cambridge. Not so in America: unless the team has a plural-sounding name, Americans treat it as singular: Harvard beats Yale. British English has a still further nicety. Manchester United are top of the Premiership. But Chelsea is the richest club. The team are plural; the club — even if its name is Rangers — is singular.

Sport can even rewrite spelling. Leafs is the correct plural when it is part of Toronto’s Maple Leafs ice-hockey team, just as Sox is correct in more than one American side.

Company names pose a problem. Most of us treat them as plural. In Britain that was helped by an accident of English orthography. In the Scottish village of my childhood, the baker was Archie Kirkwood. So his shop was Kirkwood’s. Had it grown into a mighty chain, it would no doubt have become Kirkwoods, with no apostrophe, a plural. Many Victorian firms went this way. But business journalists tend to treat company names as singular, even when they look or plainly are plural: General Motors was in trouble. That’s logical enough. But, mercifully, no one pushes this practice to its logical conclusion of General Motors’s losses were huge.

Try rolling Reliance Industries’s internal squabbles round your tongue, and you’ll see why not. Some words are singular or plural depending on the way they are used. Thus, economics is the dismal science. But the economics of rice-growing in Norway are dubious. Or, politics is no career for the squeamish. But the politics of West Bengal are... well, you supply the adjective.

At times, an apparently plural subject takes a singular verb. A million dollars is peanuts to Bill Gates; you’re thinking of the money as a unit, a sum of $1 million. Likewise, at university politics and economics is a good choice; you mean a single course, politics-and-economics. But when your young propose some bizarre combination, you will be as right in grammar as in fact to reply that, (for example) biology and art history hardly go together.

Still, logic and language seldom go together either. Witness the oddest of plural/singular oddities. It is thoroughly idiomatic — indeed, old-fashionedly so — to say these sort of criminals are a menace to society. These sort? Some old-world variant of these sorts, maybe? No: that easy explanation is in fact wrong. The phrase doesn’t mean criminals of these various sorts. It means of this one sort, the one you have just described. So why are?

I have no answer, and I’ve never met a persuasive one from experts. I don’t advise using such a phrase in an examination. But if you do, your English, however improbably, will be perfectly correct.