As nouns the difference between aab and aad

is that aab is {{initialism of |anti-aircraft battery|lang=en} while AAD is initialism of Aircraft Assignment Directive.

As proper nouns the difference between aab and aad

is that aab is any of various organizations with these initials, such as the Association of Applied Biologists while AAD is initialism of American Academy of Dentists

As a symbol AAD is

A designation on prerecorded compact discs indicating that the contents were recorded and mixed in analog before being mastered to a digital medium; compare ADD, DAD, DDD.

As an adjective aad is

old.