a part of something larger, especially a part that is different from the other parts
The front portion of the rocket breaks off.
The rent on his portion of the apartment was $500 a month.
The main character's childhood takes up a good portion of the film.
an amount of food for one person, especially when served in a restaurant [= serving, helping]:
Do you have any children's portions?
a huge portion of roast beef
He served generous portions (=large portions) of soup from a black pot.
3 [usually singular]
a share of something, such as responsibility, blame, or a duty, that is divided between a small number of people
The other driver must bear a portion of the blame for the accident.