Commentary: both James' birthday and James's birthday are grammatically correct. Remember: it's up to you! Use the version which best matches how you would pronounce it. Use James's if you pronounce it "Jamesiz", but use James' if you pronounce it "James".
Jameses, James's and James' all have their place in the English language. If you're talking about the possessive form of James you should use James's or James'.
The Associated Press Stylebook says the correct way to write the possessive case of Chris is Chris', not Chris's. Other style guides, including the Chicago Manual of Style, say Chris's is correct. If there isn't a specific guidebook you need to follow, you can use either Chris' or Chris's.
Both James' and James's are grammatically correct.
Certain academic writing styles prefer one version over the other, but it doesn't matter which one you use in your regular, written English.
For proper names like James, AP says, add an apostrophe only: He borrowed James' car. For generics like boss, add an apostrophe plus S: He borrowed the boss's car. But there's an exception: When the word that follows begins with an S, use an apostrophe only.
Like any noun ending in S, the plural adds -ES, so one James, two Jameses. For possessive, just add an apostrophe: Jameses'. This formation common for last names (“keeping up with the Joneses' spending habits”) but can also be used for first names.
The important thing to remember is that Thomas is singular. When you're talking about more than one, you first form that plural by adding -ES. One Thomas, two Thomases. Then, to note that something is owned by more than one Thomas, just take the plural and make it possessive: Thomases'.
The apostrophe has three uses: 1) to form possessive nouns; 2) to show the omission of letters; and 3) to indicate plurals of letters, numbers, and symbols. Do not use apostrophes to form possessive pronouns (i.e. his/her computer) or noun plurals that are not possessives.
Second, a name ending in s takes only an apostrophe if the possessive form is not pronounced with an extra s. Hence: Socrates' philosophy. Saint Saens' music.
To show the possessive form for a person's name ending in S, you either add an apostrophe and S ('s) or just an apostrophe ('). The rule depends on the house style manual you're following. For example, Jones can be Jones' or Jones's. James can be James' or James's.
In English, the possessive of every singular noun--even singular nouns that end in "s"--is formed by "apostrophe s" with one curious exception (which I'll get to in a moment). Thus "Joe's bike" and "Jess's bike" are both correct but "Jess' bike" is incorrect.
The possessive
Quick Use: Use an apostrophe + s for singular nouns (sea, sky), common nouns ending with s (tigress, mistress), and irregular plural nouns (women, children). Use only the apostrophe for proper nouns ending with s (Tess, Jesus, Texas) and regular plural nouns (cars, protestors).
Most Sources Say to Add -es to the End
The Chicago Manual of Style, the AP Stylebook, Garner's Modern American Usage, and the Cambridge Guide to English Usage all say to make names that end with -s plural by adding -es, and they make no exceptions for pronunciation.
required to make the proper noun possessive. correct to use both James' bag and James's bag to show possession. The main rule is that the use of apostrophes are consistent across the piece of writing.
The possessive of a singular noun is formed by adding 's (whatever the final consonant). Note that some consider Jesus to be an exception to this rule and insist that its possessive be written Jesus'; other exceptions may include other ancient proper names.
Originally Answered: Which is the correct form for plurals, "James' pen" or "James's pen”? The modern and correct handiwork is apostrophe-S for all proper nouns (names) regardless of their endings — James's pen.
The Associated Press Stylebook recommends just an apostrophe: It's Tennessee Williams' best play. But most other authorities endorse 's: Williams's. Williams's means “belonging to Williams.” It is not the plural form of Williams. People's names become plural the way most other words do.
If the name ends in s, z, ch, or sh, you need to add es. That means the Davis family becomes the Davises, the French family becomes the Frenches, the Hernandez family becomes the Hernandezes, and the Glaves family becomes the Glaveses. If the name ends in x, also add es—unless the x is silent.
Use 's for the possessive of singular nouns that end in s:
Charles's books, Dickens's novels, actress's script. Note: If a singular noun ending in s is followed by a word beginning with s, use only the apostrophe, not the 's. For example, Charles' shirt.
The most common apostrophe errors involve homonyms: words that sound like each other but are spelled differently. Let's start with Its', its and it's. Its' is never correct; it is singular, so it would never require a plural possessive. If you're indicating possession, use its—no apostrophe is ever required.
When one person owns something, we use an apostrophe and then an s. This is the most common way that apostrophes will be used, and the easiest rule to remember. If you own it, put an apostrophe on it.
Possessives. Form the possessive case of a singular noun by adding 's (even if the word ends in s). Form the possessive case of a plural noun by adding an apostrophe after the final letter if it is an s or by adding 's if the final letter is not an s. Remember: the apostrophe never designates the plural form of a noun.
Boy's name Louis, pronounced Loo-ee. Louis's. If it's pronounced Loo-ee and you don't add the final s, just the apostrophe, it would still be pronounced Loo-ee which would be wrong as a possessive - Loo-ee bag instead of Loo-ee's bag. So use the 's.