Affinity is rated dependant on strength from S - F, F meaning no affinity. Affinity is how strong you are with a certain Magia. Magia each have a deity and each has their own unique skill tree and spells. These will be elaborated on in their own pages.The rating of a magia strength can go up as you become more profficient with the type, but this takes a long time to grind and train, so most people stick with their strongest magia type.
Affinity is found out during the first public meeting of a noble, or the first time a person goes to school if they are not of high class, higher up famillies often selectively marry off their kids for the sole purpose of creating a stronger magia affinity. Nearly all people have at least one element with the affinity of C and all have one of at least D. 90% of people have an affinity of B in the Null Magia.