It seems that the exhaust valve of this engine is broken.

My mother serves food for us every day.

My mother served dinner.

He is acting based on humanitarianism.

Transitive verbs require an object that is directly moved by the subject.

He is a true humanitarian, always striving to alleviate the suffering of others.

He often thinks about problems from a humanitarian perspective.

We believe that all people should be treated based on the spirit of egalitarianism.

The theory of harmonic oscillators is a fundamental concept in physics.

Mr. Wan is my best friend.