What's a homonym?
Homonyms are two words which sound the same, but are spelled differently.
Let's look a few commonly misused homonyms:
It's vs. its; there vs. they're vs. their; let's vs. lets; you're vs. your; whose vs. who's; capital vs. capitol; principle vs. principal; passed vs. past
It's: A contraction of "it is." Do not use anywhere you would not use "It is."
ex: It's purple.
Its: The possessive of "it." Use when "it" owns something.
ex: Its hat is purple.
There: A place. Should only be used when pointing at something, or in text when "there" has been clearly specified.
ex: It is over there.
There: A way of starting a sentence in passive voice. (Why are you using passive voice in your writing? You'd better have a good reason. No, really.)
ex: There is nothing worse than getting squashed by a falling toilet.
They're: A contraction of "They are." Use only when you would use "they are."
ex: They're in Georgia.
Their: The possessive form of "they." Use when they own something.
ex: Their car broke down in Georgia.
Let's: A contraction of "let us." Use only as a substitute for "let us."
ex: Let's go to Canada.
Lets: The present tense conjugation of "let" (as a synonym for "allow") for a singular person.
ex: He lets me borrow his flour.
You're: A contraction of "you are." Use only as substitute for "you are."
ex: You're angry, aren't you?
Your: The possessive of "you." Use when you own something.
ex: Your book bag is heavy.
Whose: The possessive of "who." Use when you are trying to determine the owner of something, or when you are using "who" as a pronoun.
ex: Whose book bag is that?
ex: I gave it to Jacob, whose book bag needed the extra space.
Who's: The contraction of "who is." Use only to replace "who is."
ex: Who's responsible for the laundry this week?
Capital: A city that serves as the seat of government for an area, or an asset such as wealth, or a capital letter.
ex: Raleigh is the capital of North Carolina.
Capitol: Only used to name a building; specifically, the building in which the legislature meets.
ex: We were really bored during our tour of the Capitol Building.
Principle: A moral purpose.
ex: It's against my principles to eat raw steak.
Principal: An adjective meaning most important, or the leader of a school, or the initial investment of money before interest is added.
ex: The principal objective is to not get eaten by the dinosaurs; after that, you need to capture the flag.
Passed: The past tense of the verb "to pass." Use only if someone has physically moved from behind to ahead of something, or passed a test.
ex: I passed the test with flying colors.
ex: He passed me in the right-hand lane.
Past: A location; a time period; a preposition; an adverb; "past" locates something in time and space.
ex: I stuck my tongue out as I drove past him.
ex: One look at the funny breeches told him everything: he was stuck in the past, with no way home.
ex: In my past life, I was an osterich.
ex: The days for mourning are now past.
ex: It was half past three.
What are the most common homonym mistakes you see?