Aught is an old-fashioned word meaning “anything at all.” It appears most often in the phrase “for aught I know,” which means “for all I know” or “as far as I'm aware.”

You'll encounter this word mainly in older books and poetry. In Charles Dickens's A Christmas Carol, characters speak of things happening “for aught they cared,” meaning they didn't care one bit. When someone says “if aught should happen,” they mean “if anything should happen.”

The word creates a formal, sometimes dramatic tone. A character in a historical novel might say, “I know not aught of his whereabouts,” which is just an old-fashioned way of saying, “I don't know anything about where he is.”

Interestingly, aught can also mean the number zero, especially when naming years in the 2000s. Some people called 2008 “aught-eight” or the whole decade the “aughts,” though this usage is less common than simply saying “two thousand eight.”

Today, aught sounds archaic and poetic. You wouldn't use it in everyday conversation unless you were joking around or trying to sound like a character from a Shakespeare play.