I'm trying to get my head round how we use so called invariable plurals. I have been through about a million different sites now, and come up with the following:
(i) There are three main groups of invariable plurals, namely
a) nouns denoting things (typically garments and tools) that consist of two or several conjoined parts, such as scissors, trousers, binoculars, tweezers etc
b) nouns denoting groups of living beings, such as police, people, cattle, vermin, personnel, clergy etc
c) miscellaneous nouns ending in -s, such as arms, fireworks, belongings, oats, valuables, regards, remains, clothes etc
(ii) All three kinds of invariable plural always take plural verb form (the binoculars were very expensive), always take plural demonstratives (these binoculars are expensive) and are always replaced by plural, rather than singular anaphoric pronouns (Did you see those binoculars? They were very expensive)
Now to my questions:
Have I got things right so far? If not – where did I go wrong?
Apart from impact on choices of verb form, demonstratives and anaphors, I'd also like to know whether invariable plurals are all countable (only there can never be just one) – that is, can we use cardinals (except one) and quantifiers that normally go only with countables (e.g. many and several) with all of them? If not, can we distinguish any kind of pattern?
Is group (b) above distinct from what's generally referred to as collective nouns, or is it the same? If it's not the same, how do we tell them apart?