Question

What is the proper use of the apostrophe with a singular possessive noun ending in "S"?

Answer 1

I think the question was about an apostrophe for a possessive singular noun that already ends with an "s", like grass.

Explanation:

The are two accepted forms to show possession of a singular noun that ends with an "s":

• add and apostrophe (') after the existing "s" (grass')
• add and apostrophe s ('s) after the existing "s" (grass's)

Examples:
The grass' color indicated that it was too dry.
The grass's color indicated that it was too dry.
Put the mail on the boss' desk.
Put the mail on the boss's desk.
We took a ride in Carlos' new car.
We took a ride in Carlos's new car.

If you are a student, use the form that your teacher prefers. Otherwise use the form that you prefer. I personally prefer to use the apostrophe s ('s).