When you find it hard to remember things, that's forgetfulness. Your forgetfulness might mean you have to return home twice — to get the lunch and jacket you left behind — before running to catch the bus.
Another word for forgetfulness is absentmindedness. If your memory just isn't working the way it should, leaving you grasping for answers on your Spanish test and baffled about the name of an actor in your favorite movie, you can chalk it up to forgetfulness. Forgetfulness can also cause hurt feelings, like when you forget your best friend's birthday or forget to arrive on time for your brother's piano recital.