Aptitude (良成長, Yo seichō, lit. Good Growths in the Japanese version, Prodige in the French version, Talento in the Italian version, Promesa in Spanish version) is a skill introduced in Fire Emblem Awakening and reappears in Fire Emblem Fates. It is learned by Villagers at Level 1.
In Awakening, growth rates are boosted by 20%. If a unit's base growth rates are: 95% HP, 65% Str, 15% Mag, 65% Skl, 65% Spd, 80% Luck, 45% Def and 15% Res, then their new growth rates with Aptitude becomes: 115% HP, 85% Str, 35% Mag, 85% Skl, 85% Spd, 100% Luck, 65% Def, 35% Res. In the case of HP, they will now always gain HP every level and have a 15% chance of gaining 2 HP points instead.
The same formula is used in Fates, except Aptitude will only increase the unit's growth rates by 10%.