In physics, blackbody radiation is a very important concept.

He often uses four-kanji idioms.

Understanding the four-step conjugation in Japanese is difficult.

Koushirou is my best friend.

This box is perfectly square in shape.

This square box is very simple and beautiful.

I live in Yokkaichi.

Père David's deer, also known as the 'four unlike', is a species of deer native to China and is listed as an endangered species.

My new car is a four-wheel drive.

He likes to speak using four-character idiomatic compounds.