Magic capacity

A person's magic capacity represents his/her natural talent at spellcasting.

Someone with small capacity is still able to learn magic, but will likely be unable to use more complex spells no matter how hard he or she may study. On the other hand, capacity alone is not enough for someone to be a successful wizard. For instance, as Hajime Kanzaka explained, while Gourry Gabriev has great magic capacity, which would allow him to cast almost all the most powerful spells short of the Dragon Slave, he's still unable to use magic at all as he cannot memorize the incantations correctly.

Two measurements of a person's magic capacity exist: Bucket capacity and pool capacity. (See their respective entries for details.)