inadvertence

1. The quality or habit of being inadvertent.
2. An instance of being inadvertent; an oversight or slip.

[Middle English, from Old French, from Medieval Latin inadvertentia : Latin in-, not; see in-¹ + Medieval Latin advertentia, advertence; see advertence.]

The absence of attention or care; the failure of an individual to carefully and prudently observe the progress of a court proceeding that might have an effect upon his or her rights.

The term inadvertence is generally used in reference to a ground upon which a judgment may be set aside or vacated under the Rules of Federal Civil Procedure or state rules of civil procedure.

The noun has 2 meanings:

Meaning #1: an unintentional omission resulting from failure to notice something
  Synonym: oversight

Meaning #2: the trait of forgetting or ignoring your responsibilities
  Synonyms: unmindfulness, heedlessness, inadvertency