portion · part of · subset

For a long time, society was strongly hierarchical and unequal, primarily composed of peasants. The most backward, impoverished segment of the population, they were crushed by the weight of taxes, wars, and famines.

Your homework is one important part of the learning experience.

A portion of the proceeds will go to benefit children with disabilities.

Whenever I get a large sum of money, I donate some of it to charity.

I agree with some of your opinions.