Any reason not to use "céard" in place of "cad"?
Dialect? If you want to speak Connacht Irish, use céard. If you want to speak anything else, use cad.
I should probably already know this ..... but it's not "cad i" because the noun has a possessive pronoun? (I thought I was being pretty swift remembering that aidhm is feminine ....)
It's not í because, while the word aidhm is feminine, the actual "aim" itself may not be. "My aim is to climb that hill", "his aim is to get on the team", etc.