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Rules for Forming Plurals

Forming plurals can be tricky. But luckily, you can use several rules to guide you:

• the basic rule – The basic rule when it comes to forming plurals is to add the letter s to the singular form of the noun. This is the simplest and most straightforward rule. For example, the singular committee becomes the plural committees, league becomes leagues, menu becomes menus, and quota becomes quotas.
• rules relating to nouns ending in s, x, ch, sh, and z – When singular nouns end in s, x, ch, sh, or z, you add es to form plurals. Examples include the words businesses, faxes, sketches, and wishes. The only exception to this rule is the noun quiz. To make this plural, zes is added, forming the plural quizzes.
• rules relating to nouns ending in y – When a noun ends in a y that's preceded by a consonant, you form the plural by changing the y to an i and adding es. For example, liability becomes liabilities, copy becomes copies, and policy becomes policies. However, when a noun ending in a y is preceded by a vowel, the letter s is added to form the plural, as in the words attorneys, boys, and delays.
• rules relating to nouns ending in f, fe, and ff – You form the plurals of nouns that end in f, fe, or ff by adding s, as in tariffs, beliefs, and safes. The exceptions related to this rule refer to words such as leaves, halves, selves, and wives. These plurals are formed by changing the f or fe to ve and then adding s.
• rules relating to singular nouns ending in o – You create the plural forms of singular nouns that end in o in two ways. First, if the o is preceded by a vowel, you add an s to form words such as stereos and ratios. But if the o is preceded by a consonant, you usually add es. For instance, hero and tomato become heroes and tomatoes.

Some special rules apply to three categories of nouns:

• proper nouns, which name individual people or things and should begin with a capital letter – The main rule for forming plurals of proper nouns is that the original spelling must not be altered. All that's added to the singular noun is an s. For example, "Mr. and Mrs. McCarthy " become the McCarthys, not the McCarthies.
• foreign nouns, which have been adopted from other languages, such as Greek and Latin, into the English language – Foreign nouns use different rules to form plurals. Words ending in o in the singular sometimes change to i in the plural. For instance, concerto becomes concerti. And singular foreign nouns that end in on or um receive an a to form the plural. So, criterion becomes criteria.
• irregular nouns, which include nouns surviving from Old English – Some nouns, especially those derived from Old English, are irregular because their plurals are formed by changing letters within the word or adding letters other than the usual s or e s. You're likely to be familiar with most of these words, but in cases where you are uncertain, you should refer to your dictionary.

Another area to consider is the plurals of hyphenated and open compound nouns. For hyphenated forms, you usually add an s to the element that is being pluralized – for example, fathers-in-law. In open compounds, the same applies – for example, accounts payable, rules of thumb, and notaries public.

So, as a general rule, you attach the plural form of a compound word to the base element – the one that changes in number or the principal noun – regardless where the element falls in the term. If there is no clear principal noun, then the plural applies to the entire compound as in hand-me-downs or author critics.

The only nouns that don't form plurals are noncount nouns. You don't add s to these types of nouns. Examples include bread, equipment, respect, and information.

A common error in writing is to form plurals by adding an apostrophe s to the singular form of a noun. Remember that you use apostrophe s for possessive nouns, such as John's portfolio. It's not meant for creating plural nouns. However, you may find that certain handbooks teach the use of an apostrophe in the plural forms of numbers and letters. So, for example, in the sentence "She scored 10's in all quizzes," the score 10's contains an apostrophe, but it doesn't have to. This method of forming plurals is not formally agreed upon.

You can follow several rules for creating plurals from singular nouns. The basic rule is to add s to the singular form of the noun. When singular nouns end in s, x, ch, sh, or z, you add e s to form plurals. Nouns ending in a y that are preceded by a consonant are formed by changing the y to an i and adding es. The plurals of nouns that end in f, fe, or ff are formed by adding s.