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Sister-in-laws, sisters-in-law, or sisters-in-laws?

If you had more than one sister-in-law, how would you talk about them? Think you know? How about if you wanted to refer to more than one right of way? Would you say rights of way or rights of ways? Here are a few more plural brain-teasers:

Singular noun Plural A Plural B Plural C
father-in-law father-in-laws fathers-in-law fathers-in-laws
poet laureate poets laureate poets laureates poet laureates
governor-elect governors-elects governor-elects governors-elect
attorney general attorneys general attorneys generals attorney generals
passer-by passer-bys passers-by passers-bys

A clue: there’s sometimes more than one accepted form (the answers are revealed at the end*).

Overall, the formation of plural nouns in English spans the spectrum of straightforward to tricky: there’s a handy guide here to the basics. Thankfully, you can pluralize many one-word nouns simply by adding a final ‘s’. On the other hand, there are some thornier cases which need more care: one of these is how to form plurals of words that entered English from other languages, about which I’ve posted before.

As you might have gathered from tackling the above mini-test, a further common area of perplexity is the pluralization of some compound nouns, that is, nouns made up of two or more existing words, of which father-in-law is an example. Such nouns can be written in three different ways:

1. As one word (called a closed compound): footstep, schoolchild, bookcase.

2. As two or more separate words (known as an open compound): table lamp, nuclear family, right of way.

3. With a hyphen or hyphens: build-up, lady-in-waiting, brain-teaser, yes-man.

As the focus here is on plurals rather than spelling, I’m not going to discuss the whys and wherefores of hyphenation versus open or closed forms. Instead, let’s look at some rules for forming the plurals of compounds. The good news is that for many such nouns, all you need do to make the plural is to think about how the final word is pluralized and follow the same rules. You can apply these rules regardless of how the compound is written.

Rule 1: add an ‘s’ to the end

As mentioned at the outset, most nouns form their plurals by adding an ‘s’ to the end, and you can apply this rule to many compound nouns. For example, because you pluralize lamp, step, and teaser by adding an ‘s’ to the end, if you want to talk about more than one table lamp, footstep, or brain-teaser, just add an ‘s’ to the end of the compound (table lamps; footsteps; brain-teasers).

Rule 2: if the final element has an irregular plural, use that

Not all nouns form their plural by adding an ‘s’. If the final word or element of a compound is pluralized in a different way (e.g. child children; family → families; man  men), just use that form for the plural of the compound (schoolchildren; nuclear families; yes-men).

Rule 3: identify and pluralize the noun

Some compounds consist of a main noun together with a word or word group which doesn’t have a plural in English, such as an adjective (attorney general), a preposition (passer-by), or a prepositional phrase (lady-in-waiting). Honing up your analytical word-class (part of speech) skills is the key to understanding how to pluralize such compounds.

a) Compounds containing postpositive adjectives

There’s a set of compound nouns which are formed from a noun followed by a postpositive adjective. A postpositive adjective is one that follows the noun rather than precedes it: examples are heir apparent, attorney general, and president-elect. This pattern, which goes against the grain of typical English syntax (in which adjectives come before nouns: a large house; a sweet child), is due to the historical influence of French on English from the Norman Conquest onwards.

So heir, attorney, and president in the examples above are nouns, with apparent, general, and elect being adjectives. The general rule for this type of compound is that you pluralize the nouns in the normal way and leave the adjectives as they are: heirs apparent; attorneys general; presidents-elect.

But….see Rule 4 below for a caveat to applying this rule wholesale.

b) Compounds containing a noun and a preposition

Some common examples of these compounds are words such as passer-by, hanger-on, and washer-up, in which the noun element ends in -er and is followed by a preposition. Plurals are formed by adding an ‘s’ to the noun: passers-by; hangers-on; washers-up.

However, other compound nouns ending with a preposition are typically formed from a verb plus a preposition. Examples are build-up, set-to, add-on, and lay-by. Their plurals follow Rule 1 above – that is, you add an ‘s’ to the final element of the compound: build-ups; set-tos; add-ons; lay-bys.

c) Compounds containing a prepositional phrase

All the ‘-in-law’ words (e.g. son-in-law, mother-in-law) come into this category, as do compound nouns such as maid of honour, man about town, editor-in-chief, and right of way.

The rule to follow with such words is to pluralize the main noun and leave the prepositional phrase unaltered: sons-in-law; maids of honour; men about town; editors-in-chief; rights of way

Rule 4: use a dictionary

All spellings in any good dictionary are based on the evidence of the living, changing language, which lexicographers constantly monitor. In the case of Oxford Dictionaries, lexicographers trawl through vast databases such as the Oxford English Corpus (OEC) tracking developments in spelling (as well as in meaning, of course). Over time, accepted usage changes, and lexicographers amend dictionary entries accordingly. This accounts for the fact that some of the compounds discussed here have more than one plural in the dictionary.

Let’s take the case of compounds having postpositive adjectives. Because many people aren’t aware that the final words in these compounds are adjectives, forms such as court martials and poet laureates have now become established through usage as alternative plurals and you’ll find them in the dictionary.

Other plurals could be gaining ground too: passers-by (also spelled passersby) is currently the standard plural, with 5,481 occurrences on the OEC. At present, the OEC only records 71 instances of passerbys or passer-bys (1.3%). These examples are found in British, American, Irish, East Asian, and Indian English and crop up in edited writing such as news reports, as well as in unedited blogs and similar sources. Lexicographers will track these changes, and if they see a significant rise in the form passer-bys that indicates it’s becoming part of accepted usage, then it could gain inclusion as an alternative plural in the future.

To sum up, the rules are a useful guide, but remember that language never stands still and most rules worth their salt have an exception, so keep a dictionary handy if you’re not sure. Happy pluralizing!

*Test answers

Singular noun Plural
court martial courts martial or court martials
father-in-law fathers-in-law
poet laureate poets laureate or poet laureates
governor-elect governors-elect
attorney general attorneys general
passer-by passers-by

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