...an absent-mindedness...

is where a person shows inattentive or forgetful behaviour. It can have three different causes:

1. a low level of attention ("blanking" or "zoning out")
2. intense attention to a single object of focus (hyperfocus) that makes a person oblivious to events around him or her; or
3. unwarranted distraction of attention from the object of focus by irrelevant thoughts or environmental events.

Absent-mindedness is a mental condition in which the subject experiences low levels of attention and frequent distraction. Absent-mindedness is not a diagnosed condition but rather a symptom of boredom and sleepiness which people experience in their daily lives.
When suffering from absent-mindedness, people tend to show signs of memory lapse and weak recollection of recently occurring events. This can usually be a result of a variety of other conditions often diagnosed by clinicians such as ADD and depression.
In addition to absent-mindedness leading to an array of consequences affecting daily life, it can have as more severe, long-term problems.