He is majoring in chemistry at university.

He is an expert in chemistry.

This lake is known as a dangerous body of water.

This lemon is sour.

Please add a little vinegar to this salad.

Please use the emergency stairs in case of a fire.

Due to the earthquake, the city declared a state of emergency.

This food may contain carcinogens.

We exist as a part of the material world.

Antibiotics don't work for colds, so please don't take them unnecessarily.