In the world of Santa's workshop, an adult elf is generally considered to be one who has reached the age of 18 or 21, depending on local laws and customs. However, in the magical world of Christmas, age is a fluid concept, and some elves may consider themselves adults at a younger age, while others may feel they are still children at a much older age. Ultimately, the determination of adulthood is a personal choice, and each elf is free to define it for themselves in their own unique way.