This is my new bag.

He is my friend.

'Apple' is a count noun, and you can count it as one, two, etc.

Peroxides play an important role in chemical reactions.

A count noun, or 'kasu meishi', represents something that can be counted.

There are many earthworms in this soil.

Ishimori is my best friend.

My father is a doctor.

Mr. Ishiyama is my best friend.

The cornerstone of this building is very strong.