Scatterbrain (noun)

A person who is forgetful, inattentive, and easily distracted.

Origin:

Early 17th century: from scatter + brain.

Examples:

1. I'm such a scatterbrain, I always forget my keys.
2. He"s a scatterbrain and can"t seem to focus on anything for more than a few minutes.
3. She's always been a scatterbrain, leaving things behind wherever she goes.
4. He"s a scatterbrain and can"t seem to focus on anything for more than a few minutes.
5. Scatterbrain, scatterbrained, or scatter-brained refers to a person who is forgetful, inattentive, and easily distracted.