Yours. Mine. Ours. Whether You’re negotiating with a toddler in the kitchen or engaging in literary criticism at the coffee shop, chances are you use possessive nouns every day without giving them a second thought. Writing them down, though, can be a little more complicated. Over the next few installments of the Writer’s Toolbox we’ll look at possessive nouns and pin down just where to put that tricky little apostrophe. This week we’ll focus on the basics: how to form the possessive for most singular common nouns, including those ending in s.

A Refresher
First, a few quick definitions. A noun is a person, place, thing, or concept; it does not need to be tangible. A proper noun is a noun that names a specific person, place, business, book, etc. Nouns that are not specific names (proper nouns) are common nouns. For example, Alberta, Burger King, and Alanis Morissette are all proper nouns; book, article, and course are common nouns.

A singular noun refers to one; a plural noun, more than one. Book and article are singular, while women, bosses, and stars are all plural. In this week’s installment, we’ll focus on forming the possessive with singular common nouns. Plural nouns and proper nouns will appear in future columns.

General rule for singular common nouns
For most singular nouns?like book, article, and course?the general rule is to form the possessive by adding an apostrophe + s.

Example A: The student’s research turned up interesting data.

A caution: a noun with an apostrophe + s is always, always either a possessive singular noun or a contraction (usually standing in for the noun + is). Never use the apostrophe + s to form the plural.

Example B (incorrect): Our customer’s are always right. This is incorrect because the possessive form of the noun has no place in this sentence.

Example C (correct): Our customers are always right. This is the proper plural form.

Example D (correct): Our customers? complaints are responded to personally. This is proper plural possessive form, which will be addressed in a future issue.

Example E (correct): We had only one customer today, and that customer’s attitude was very unpleasant. This is singular possessive form and is correct because it is referring to the attitude of one single customer.

Singular nouns ending in –s

But what about singular common nouns that already end in –s, like boss, grass, and illness? Most of the time, these follow the general rule, forming the possessive by adding an apostrophe + s.

Example F: My boss’s attitude is lowering my self-esteem.

Example G: I found the grass’s texture rather prickly.

Note that I said ?most of the time.? There is a major exception that comes into play for singular nouns that end in –s AND that are followed by a word beginning with a s, sh, or similar sound.

And here is where things get even trickier; whether that exception even applies depends on what style guide You’re following.

If You’re following Chicago style, which is used in fiction and some academic fields, you follow the general rule and add apostrophe + s, even when a word ending in -s is followed by a word beginning with an s or sh sound.

Example H (correct, Chicago style): My boss’s statement was hurtful.

However, if You’re following AP style, which is used in publications, and you have a word ending in -s That’s followed by a word beginning with an s or sh sound, you form the possessive by adding an apostrophe only.

Example I (correct, AP style): My boss? statement was hurtful.

What about Canadian style? While Canadian style guides don’t make a formal statement other than advising users to use only the apostrophe if it would sound ?difficult? or ?awkward? when pronounced aloud, in practice Canadian style aligns itself with the AP style exception.

Confused? don’t be; just remember that this style-related exception only comes into play when a singular common noun ending in -s is followed by a word beginning with an s sound?and even then, it only applies if You’re using AP or Canadian style. Otherwise, add the apostrophe + s regardless of what style guide You’re using.

The world of possessives can seem confusing, but breaking it down into smaller parts makes it more manageable. A recap of this week: if you have a singular common noun that does not end in -s, you form the possessive by adding an apostrophe + s. If you have a singular common that does end in -s, you still follow the general rule and add the apostrophe + s, unless the word that follows it starts with an s or sh sound AND You’re following AP or Canadian style. Memorize it, put it on a cheat sheet, or both.

Next week we’ll move on to plural nouns and examine how to form plural possessives, where to put the apostrophe, and how to keep from getting plural and singular possessive mixed up. Save room on your cheat sheet for these rules and for future installments on proper nouns and exceptions to the rules.

Christina M. Frey is a book editor and a lover of great writing. Chat with her on Twitter about all things literary @turntopage2.