He studied history to understand the labor hardships experienced by ancient people.

He injured his arm in a workplace accident.

We need more labor force to make this project successful.

The labor market situation is tough.

My father is the leader of a labor union.

He was able to escape from the situation of forced labor.

The foundation stone of this building was laid 100 years ago.

Compounds containing acyl groups play an important role in organic chemistry.

The allyl group plays an important role in organic chemistry.

The sulfonyl group plays an important role in chemical reactions.