Nouns of this group are occasionally understood as plurals:
Their tactics requires/reguire concentration of troops.
Politics has/have always interested me.
Plural invariable nouns
§ 176. Plural invariable nouns comprise two types - marked and unmarked plurals.
I. In the first type the form of the noun itself shows plurality. These nouns are rather numerous. Semantically they fall into several groups:
a) names of tools or articles of dress consisting of two equal parts which are joined: bellows, binoculars, breeches, braces, flannels, glasses, pants, pincers, pliers, pyjamas, scales, scissors, shorts, spectacles, suspenders, tights, tongs, trousers, tweeters;
These nouns can be made singular and countable by means of a pair of: a pair of trousers, a pair of scissors. Accordingly they are used with the verb-predicate in the singular (this pair of trousers is ...)
b) miscellaneous nouns: annals, antics, archives, arms, ashes, the Commons (the House of Commons), contents, customs, customs-duty, customs-house, earnings, goods, goods train, greens, holidays, summer-holidays, manners, minutes (of the meeting), outskirts, quarters, headquarters, stairs, suds, surroundings, thanks, troops, wages, whereabouts, the Middle Ages;
c) some proper nouns: the East Indies, the West Indies, the Hebrides, the Highlands, the Midlands, the Netherlands.
II. In the second type of the plural invariable nouns the meaning of plurality is not marked in any form (hence the term “unmarked plural invariables”). They are usually treated as collective nouns (собирательные).
English collective nouns denote only living beings (family, police, clergy, cattle, poultry, etc.) and have two categorical meanings: the first - plurality as indivisible whole and the second - discrete plurality, that is plurality denoting separate beings. In the latter case these nouns are callednouns of multitude. Thus, one and the same noun may be a collective noun proper and a noun of multitude.
The difference in two categorical meanings is indicated by the number of the verb-predicate (singular in the first case and plural in the second), as well as by possessive and personal pronouns. The meaning of the predicate is also important: predicates denoting physiological processes or states, emotional or psychic reactions, states always imply separate beings involved into it. Compare the following examples:
Collective nouns proper
Nouns of multitude
The familywas large
The cattleis in the mountains
The crew on the shipwas excellent.
The crowdwas enormous.
The committeewas unanimous.
The familywere fond oftheir house.
The cattleare grasing there.
The crewhave taken their posts.
The crowdwere watching the scene spell-bound.
The committeewere divided in their opinion.
Discrete plurality is also expressed by substantivized adjectives denoting people:
the helpless, the needy, the poor, the sick, the weary, the rich.