To omit means to leave something out, either on purpose or by accident. When you omit vegetables from your sandwich, you're choosing not to include them. When a student omits their name from the top of a test paper, they've forgotten to write it down.

Writers omit details from stories all the time, choosing what to include and what to skip. If you're retelling what happened at recess but omit the part where you tripped, you're deliberately leaving that detail out. Sometimes omissions are innocent: you might omit a friend's name from a party invitation list simply because you ran out of envelopes. Other times, omitting information can be misleading, like when someone describes a movie but omits all the scary parts to convince you to watch it.

The word often appears in instructions: “Omit questions 5-7 if you're in the beginner group.” That means skip those questions entirely. An omission is something that's been left out, whether accidentally or deliberately. If you notice an omission in your homework, you've spotted something missing that should be there.