Plural Forms
The plural form of most nouns is created simply by adding the letter s. Words that end in -ch, x, s or s-like sounds, however, will require an -es for the plural: In addition, there are several nouns that have irregular plural forms.
Problem Children
Many careful writers insist that the words data and media are Latin plurals and must, therefore, be used as plural words. The singular Latin forms of these words, however, are seldom used: datum as a single bit of information or medium as a single means of communication. Many authorities nowadays approve sentences like My data is lost. and The media is out to get the President.

Alumni and alumnae remain problematic. The plural of masculine singular alumnus is alumni; the plural of feminine singular alumna is alumnae. In traditional Latin, the masculine plural form, alumni, could include both genders. This does not go over well with some female alums. We note, furthermore, that Vassar College, which now has both, has lists of alumni and alumnae. Hartford College for Women, we assume, has only alumnae. The word graduates and the truncated alum have much to commend them.


Special cases of plural nouns
With words that end in a consonant and a y, you'll need to change the y to an i and add es. Words that end in o create special problems. Plurals of words that end in -f or -fe usually change the f sound to a v sound and add s or -es. There are, however, exceptions: Possessive Forms
Showing possession in English is a relatively easy matter (believe it or not). By adding an apostrophe and an s we can manage to transform most singular nouns into their possessive form: Some writers will say that the -s after Charles' is not necessary and that adding only the apostrophe (Charles' car) will suffice to show possession. Consistency is the key here: if you choose not to add the -s after a noun that already ends in s, do so consistently throughout your text. William Strunk's Elements of Style recommends adding the 's. You will find that some nouns, especially proper nouns, turn into clumsy beasts when you add another s: "That's old Mrs. Chambers's estate." In that case, you're better off with "Mrs. Chambers' estate."

There is another way around this problem of klunky possessives: using the "of phrase" to show possession. For instance, we would probably say the "constitution of Illinois," as opposed to "Illinois' (or Illinois's ??) constitution."

For reasons not immediately clear to mere mortals, it is considered bad form to use apostrophe-s type possessives with pieces of furniture and buildings. Instead of "the desk's edge," then, we would say "the edge of the desk" and instead of "the hotel's windows" we would say "the windows of the hotel."

Remember that personal pronouns create special problems in the formation of possessives.

Possessive forms are frequently modifiers for verb forms used as nouns, or gerunds. Using the possessive will affect how we read the sentence. For instance, "I'm worried about Joe running in the park after dark" means that I'm worried about Joe and the fact that he runs in the park after dark present participle modifying Joe). On the other hand, "I'm worried about Joe's running in the park after dark" puts the emphasis on the running that Joe is doing ("running" is a gerund, and "Joe's" modifies that verbal).

Most plural nouns already end in s. To create their possessive, simply add an apostrophe after the s:

With nouns whose plurals are irregular, however, you will need to add an apostrophe followed by an s to create the possessive form.

When you are showing possession with compounded nouns, the apostrophe's placement depends on whether the nouns are acting separately or together.

We use an apostrophe to create plural forms in two limited situations: for pluralized letters of the alphabet and when we are trying to create the plural form of a word that refers to the word itself. Here we also should italicize this "word as word," but not the 's ending that belongs to it.