Health is very important.

His opinion is very important.

This compound was made by the chemical combination of two different elements.

These two elements chemically combine to create a new substance.

He is majoring in chemistry at university.

This chemical reacts when heat is added.

This chemical reaction is very dangerous.

He is an expert in chemistry.

He received the letter challenging him to a duel and began preparing for the duel.

Gender roles are an important element in defining individual behavior in society.