(Homonym: ad)
1. To constitute an addition.
2. To make an addition (to); join with others; increase by another or several.
3. To make an addition by combining numbers; SYN. add together.
4. To state or say further; SYN. append, supply.
5. Determine the sum of
6. Bestow a quality on

1 American Dialect Dictionary
2 attention deficit disorder
A condition (mostly in boys) characterized by behavioral and learning disorders