absentmindedness
n. B2 Upper Intermediate ab·sent·mind·ed·ness
n. the habit of forgetting things or not paying enough attention to what is happening around you. You might do this when you are thinking about something else.
n. the state of being forgetful or inattentive, often resulting from a lack of concentration or a preoccupation with other thoughts.
His constant absentmindedness leads to many small mistakes.
The professor's absentmindedness was famous; he would often leave his keys in the classroom or forget to wear his glasses.
While some view his absentmindedness as a charming quirk, others find it frustrating when he fails to follow basic safety protocols or lose important documents.