forgetfulness
1. [ noun ] (psychology) tendency to forget
Related terms: amnesia senior_moment
2. [ noun ] (psychology) unawareness caused by neglectful or heedless failure to remember
Examples:

"his forgetfulness increased as he grew older"

Related terms: unknowingness obliviousness
Similar spelling:   forgetfully
  forgetful_person
  forgettable
  frightfulness