Kazuto-kun is my best friend.

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.

A negative number refers to a number less than zero.

A positive number is a number greater than zero.

This shape is a parallelogram.

The history of the Empire of Japan is very interesting.

She is a famous numerologist, and many people seek her advice.

Please teach me how to find the greatest common divisor.