Many people are so spooked by apostrophes that a word like “they’re” seems to them as if it might mean almost anything. In fact, it’s always a contraction of “they are.” If you’ve written “they’re,” ask yourself whether you can substitute “they are.” If not, you’ve made a mistake. “Their” is a possessive pronoun like “her” or “our” “They eat their hotdogs with sauerkraut.”

Everything else is “there.” “There goes the ball, out of the park! See it? Right there! There aren’t very many home runs like that.” “Thier” is a common misspelling, but you can avoid it by remembering that “they” and “their” begin with the same three letters. Another hint: “there” has “here” buried inside it to remind you it refers to place, while “their” has “heir” buried in it to remind you that it has to do with possession.

Although “there’s” is a standard abbreviation of “there is” it is nonstandard to use “ther’re” as a written abbreviation of “there are.” People who use this nonstandard form often mistakenly use “they’re” (“they’re a lot of people coming to the party”) or even “their” (“their a lot of people”).