An irrational number is a number that cannot be expressed as a fraction.

Masakazu is my best friend.

Kazuo is my best friend.

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.

He likes to take a walk in the park at dusk.