noun
one person's portion; serving for one
Used for food, ingredients, or allocated amounts intended for a single person.
このレシピは一人分の材料です。
This recipe is for one serving of ingredients.
一人分のケーキを買ってきた。
I bought a single-serving cake.
一人前 also means 'one portion' but often implies a full, proper serving or a person's full share, and can mean 'full-fledged' or 'adult'.
Compound of 一人 (ひとり, 'one person') + 分 (ぶん, 'portion, share').