Webster's Revised Unabridged Dictionary · 1913

Omission

Omission , noun

[Latin omissio: compare French omission. See Omit.]

1.
The act of omitting; neglect or failure to do something required by propriety or duty.
The most natural division of all offenses is into those of omission and those of commission. — Addison
2.
That which is omitted or is left undone.