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.

He was the first discoverer of that new species of plant.

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

My mother prepares a traditional Japanese meal every day.

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

He is recognized as the top person in that field.

Three days ago, I went to Tokyo.

World War I was a large-scale war that lasted from 1914 to 1918.