The thirty-first day is my birthday.

We have our wedding on the twenty-first day of the month.

Polyandry is a social system where one woman marries multiple men.

The Tokyo metropolitan region is the center of Japan's economy.

Among polyandrous animals, there are species where one female mates with multiple males.

This orrery accurately reproduces the movements of the planets in the solar system.

There is an old legend in this village.

Nitrogen makes up about 78% of the Earth's atmosphere.

I boiled water using the '爨'.

There are many rice plants growing in the paddy field.