Hello[edit]

What's up.

When it is okay to use an apostrophe:[edit]

After singular nouns, before the possessive "s" - The cat's meow, the guardsman's steel balls.
- Same with nouns already ending in "s" - The Jones's private jet.
When indicating a missing letter or letters - Don't, it's (WHEN YOU MEAN "IT IS"), haven't.
At the end of compound words - The God-Emperor's throne.
When pluralizing lowercase letters - "There are two m's, two t's, and two e's in committee."

In any possessive pronoun. "What is that on the front of your bolter? Oh, that is its barrel." The act of "its" in this context being a possessive pronoun shows - wouldn't you know it - possession already, and the added apostrophe is redundant.
- Other possessive pronouns are his, hers, theirs, yours, etc. No apostrophes here for most cases.
When pluralizing uppercase letters or symbols, or dates, or other shit like that - "The 1990s were a pretty bad year for music."
- However, it's okay to use one when you cut out the first two numbers in a year, because that's elision - "The '90s were a bad year for music."

Not every word ending in "s" deserves a goddamned apostrophe.