He is an expert in chemistry.

He is using that coat from winter to spring.

You need to use your head to solve this problem.

I often go birdwatching in the park on weekends.

He committed another crime while on probation.

His body showed a rejection reaction to the transplanted organ.

His single word triggered a chain reaction, and everything changed.

She overreacted to his words.

Nuclear reactions are used for mass production of energy.

I was surprised by his overreaction.