Definition of “portion” - Learner’s Dictionary

portion

noun [ C ] uk us /ˈpɔːʃən/
PART

a part of something:

A large portion of their profits go straight back into new projects.
FOOD

B2 the amount of food served to one person, especially in a restaurant:

Breakfast was delicious - and the portions were huge!

(Definition of “portion” from the Cambridge Learner's Dictionary © Cambridge University Press)