This paper is a perfect square.

Japan's feudal system was the foundation of the socio-economic structure in the Middle Ages.

This table is tetragon in shape.

He wrote his name on the paper.

This plan was perfectly successful.

Feudalism dominated medieval European society.

You can see a beautiful view from this rectangular window.

He carefully stored the sacred sword.

He is scheduled to have surgery for phimosis.

He decided to have surgery for phimosis.