Omission means leaving something out, or failing to do something that should be done.

Basic meaning

  • In everyday English, omission is the act of not including something or not doing something.
  • It can be either accidental (you simply forgot) or intentional (you chose not to mention or do it).

Simple examples

  • Leaving an important detail out of a story or document is an omission of information.
  • Not inviting someone who normally would be invited can be described as that person’s omission from the list.

In law and duties

  • In legal or formal contexts, omission often means failing to perform a duty or required action.
  • Some offences can be committed by omission, such as neglecting a legal duty to act when required.

“Lying by omission”

  • People sometimes talk about “lying by omission,” meaning you technically tell no falsehoods but leave out key facts so the overall impression is misleading.
  • There is debate about whether omission is the same as lying, but many see serious omissions as equally dishonest or harmful.

Related words

  • The verb omit means “to leave out” or “to fail to do.”
  • Things that are left out are often called omissions in writing, speech, lists, or official documents.