Ability x (アビリティx, Abiriti x?), better known as Ability x3 and Ability x4, are Support abilities exclusive to Final Fantasy VIII. They are abilities that, while a GF has them learned, allows a character equipped with the GF to equip one or two additional abilities than normal.
Ability x3 comes with the GFs Diablos, Carbuncle, Cerberus, and Alexander, and cannot be obtained any other way. Ability x4 comes with the GF Bahamut, or can be taught to any GF by using a Rosetta Stone item on them.