He was counting money all day long.

He has difficulty expressing his emotions in words.

He showed his gratitude on his face.

My grandfather used to raise domestic silkworms and make silk.

Peroxidation is one of the chemical reactions, especially involved in the oxidation of lipids.

This apple is a countable noun.

I'm taking care of my health by having an extra meal every day.

He is good at adding numbers.

He is good at solving addition problems.

A noun is one of the main elements of a sentence.