1. the act of leaving out or failing to include something
2. something that has been left out or not included
3. the failure to do something that should be done

Examples

• The omission of her name from the list was clearly an error.
• His report contained several important omissions.
• The omission of safety procedures led to the accident.
• She noticed the omission immediately when reviewing the document.
• The contract had a significant omission regarding payment terms.
• His omission to lock the door resulted in the theft.
• The teacher marked points off for omissions in the essay.