forgetfulness

n. tendency to forget; carelessness, disregard; thoughtlessness

Forgetting (retention loss) refers to the apparent loss of information already encoded and stored in an individual's long term memory. It is a spontaneous or gradual process in which old memories are unable to be recalled from memory storage. It is subject to delicately balanced optimization that ensures that relevant memories are recalled. Forgetting can be reduced by repetition and/or more elaborate cognitive processing of information. Reviewing information in ways that involve active retrieval seems to slow the rate of forgetting.
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Noun
1. tendency to forget
(hypernym) amnesia, memory loss, blackout
(hyponym) senior moment
2. unawareness caused by neglectful or heedless failure to remember; "his forgetfulness increased as he grew older"
(hypernym) unknowingness, unawareness
(hyponym) obliviousness, oblivion

(n.)
The quality of being forgetful; prononess to let slip from the mind.
  

(n.)
Loss of remembrance or recollection; a ceasing to remember; oblivion.
  

(n.)
Failure to bear in mind; careless omission; inattention; as, forgetfulness of duty.
  

forgetfulness; he that is forgotten
  

forgetfulness; desertion