Nouns have many forms
Changing a noun from the singular to the plural may involve the mere addition of the suffix –s or –es. However, there are many nouns which form the plural in other ways, e.g. ox/oxen, child/children, tooth/teeth, die/dice, mouse/mice, knife/knives, man/men.
To compound the confusion, one needs to beware the pitfalls with nouns derived from other languages – both the singular and the plural are, almost always, as in the original language.
From Greek, we have criterion/criteria, phenomenon/phenomena, stigma/stigmata, octopus/octopodes (although octopuses is the usual form used in English), phalanx/phalanges, crisis/crises (pronounced “kraiseez”), analysis (noun)/analyses (noun, pronounced “analiseez”).
Latin contributed alumnus/alumni (masculine), alumna/alumnae (feminine), bacterium/bacteria, fungus/fungi, cactus/cacti (although cactuses is also acceptable in English), axis/axes (pronounced “akseez”), index/indices (pronounced “indiseez”, although indexes is also acceptable).
Hebrew contributed kibbutz/kibbutzim, cherub/cherubim (although cherubs is also acceptable); Arabic fellah/fellahin, mujahid/mujahidin; French bureau/bureaux, tableau/tableaux; Italian libretto/libretti, paparazzo/paparazzi.
Let us get back to English. Even though we have seen the possible variations in the formation of plural nouns, we must take care to recognise nouns which exist only in the singular, those which exist only in the plural, those which are both singular and plural, and so on.
Nouns only in singular form: These are nouns that do not have the plural form. Words like apparels, attires, equipments, furnitures, luggages are unacceptable.
Nouns singular in form but used both ways: These are nouns which are singular in form, do not have the plural form, but can be used in both the singular and the plural, e.g. aircraft, boar (boars is rare), carp, craft, deer, offspring, sheep, spawn, steer.
When one occasionally sees a report of some politician releasing fish fries (my underscoring!) into a pond, one should read fry (meaning “freshly hatched or young fish”) and not fries (meaning “French fries, or deep-fried potato chips”).
Noun plural in form but can form the plural: This is the example of summons which is plural in form but is actually singular in number. It forms the plural in the usual way (summonses, e.g. he has received three summonses since last month).
Nouns plural in form but singular in meaning: There is a group of nouns which are plural in form but are singular in meaning – and are used only in the singular, e.g. crossroads (he soon came to a crossroads), gallows, news (this is the 7 o’clock news), shambles (his room is often in a shambles).
Nouns which are plural in form and in usage: Such nouns, whose meaning is associated with only the plural form, do not have the singular form, e.g. arrears, doldrums, goods (the goods have arrived), remains (his remains were cremated), tidings, throes.
“Paired” nouns: These are nouns which are plural in form and in construction (being made up of two inseparable parts) and are used with the phrase “pair of”, e.g. scissors, trousers. (Note: the singular form is used as an adjective, e.g. trouser pocket).
Apart from the above nouns, there are nouns with singular and plural forms which, significantly, have different meanings. Examples are:
* fish/fishes and fruit/fruits (the singular is used in a generic sense, the plural is used to refer to individuals);
* desert/deserts (pronounced “dezert/dizerts”, the former meaning “an arid, barren place”, the latter “that which a person deserves as a reward or punishment”);
* due/dues (the singular form means “that which is owed as a debt or obligation” while the plural form means “a fee or charge such as for membership of a club or for enrolment in a university”;
* premise/premises (the former means “an underlying assumption as a basis for inference” while the latter means “a house or building, together with its land and outbuildings”);
* spectacle/spectacles (spectacle means “a visually striking display” while spectacles means “a pair of lenses set in a frame and used to correct one’s eyesight”).
And then there are group nouns, also called collective nouns – but that is another story.
I should like to conclude with this observation. Children grow up to distinguish the right from the left; conscionable people know right from wrong; and the recent general election tells us that the electorate are beginning to exercise their rights.