noun
omission
uh-MISH-un/əˈmɪʃn/
The act of leaving something out or something left out.
The missing number three is an omission in the sequence.

Etymology
“Let go,” with a prefix that may be intensive, developed the figurative sense “lay aside, disregard.” An omission is the act or result of leaving something out.
In context
Having forgotten to mention this, when she had last seen Sergeant Cuff, my mistress now desired me to supply the omission.
More examples
- She checks the report for errors and omissions.
- His silence is a deliberate omission of an important fact.
- The missing date is the document's most serious omission.
Forms
omission · omissions
Similar words
- exclusion
- May imply deliberately keeping something out rather than accidentally leaving it out.
- oversight
- An oversight is an accidental failure to notice or include; an omission can also be deliberate.