Academic: MLA says either, but generally 's. Chicago says either, preferring 's. APA says 's, except "You should use an apostrophe only with the singular form of names ending in unpronounced s (e.g., Descartes' theory)."
This is Travis's house. (correct and sounds better) This is Travis' house. (correct but awkward-sounding)
travis (plural traves or travises)
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.
The rule that is used for 's' is that a suffix of 'es' is added to make it plural. This is the same rule that is applied to ch, sh, s, x, and z. So, the plural of the word 'Perez' is written is 'Perezes'.
But what if the name is Sanchez or Church or Williams? Rule: To show the plural of a name that ends in s, ch, or z, add es. Examples: The Sanchezes will be over soon.
Martinez is a singular noun & Martinez's is the singular possessive form of the noun. For example, you would say “Mr. Martinez was my favorite high school teacher” or “I got to school early and stole Mr. Martinez's parking spot.”
If you're going with The Associated Press Stylebook, James' is the correct way of writing James in the possessive form. But, for all other style guides, James's is the way to go.
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).
According to the Chicago Manual of Style (which folks in my profession refer to as the Bible of Book Publishing), the rule is the same as any other singular possessive. You write her name with possession just like you say it: Alexis's. (Yes, I know it looks funny to those of us who aren't editors.)
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.
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.
Possessive forms of plural nouns
The possessive case of plural nouns that end in s is formed by adding an apostrophe: This is the boys' bedroom. My parents' house is a lovely old one.
The possessive form of almost all proper names is formed by adding apostrophe and s to a singular or apostrophe alone to a plural. By this style rule, you would express the plural of Ross as Ross's.
John Brooks is a singular proper noun and as a possessive is either John Brooks' or John Brooks's.
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.
For example, should you use “Adams' (2013) work” or “Adams's (2013) work”? Per APA Style, the answer is that the possessive of a singular name is formed by adding an apostrophe and an s, even when the name ends in s (see p. 96 in the sixth edition of the Publication Manual).
To show possession using an apostrophe, add 's for individuals (“Smith's car”) and just the apostrophe after the s for plurals (“the Smiths' car,” “the Martinezes' dog”). By convention, names from classical mythology and the Bible ending in s show possession with the apostrophe only (“Jesus' teachings”).
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.
“I visited Thomas's house” and “I visited Thomas' house” are both valid style choices. But the former is more popular in professional publishing. So a safe solution is to treat singular nouns ending in S the same way you treat singulars nouns not ending in S: Form the possessive with an apostrophe and an 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 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.
Two people can share ownership of many items and the apostrophe is still used only once. Here, Fran and Liz own all the horses together: At the farm, we rode Fran and Liz's horses.
Only use an apostrophe when you want to make a name possessive. ("From The Smith's" is always wrong, but "The party is at the Smiths' house" is correct.) This gets tricky if the last name ends in the letter "s." To make a last name that ends in "s" plural, add "es" (so Reeves becomes Reeveses).
According to Grammarbook.com, the nerds of the world will argue heatedly on the subject for eternity, but the most roundly accepted rule is to include the apostrophe, along with an extra “S.” (Davis's rather than Davis').