Kazuo is my best friend.

The children were having fun playing a counting game in the park.

The children were playing a counting game in the park.

The dual number does not exist in English grammar.

I learned about Avogadro's number in chemistry class.

We need to calculate the aggregation number of this compound.

Number theory is a branch of mathematics that primarily studies the properties of integers.

Numerology is the study of deciphering the secret meanings of numbers.

She is interested in numerology and wants to know her destiny.

A negative number refers to a number less than zero.