Changes in the social system inevitably occur with time.

This system is necessary to maintain social fairness.

I am interested in the history of the Middle Ages.

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

This table is tetragon in shape.

We plan to hold the meeting in Western European Time.

We should take responsibility as part of society.

Feudalism dominated medieval European society.

You can see a beautiful view from this rectangular window.

He carefully stored the sacred sword.