Tritium is one of the radioactive isotopes.

I read the Three Character Classic every day.

My birthday is on the thirty-first.

My father is thirty-five years old.

My father is thirty-eight years old.

It is thirty-seven kilometers to my house.

My family consists of thirty-six people.

We have our wedding on the thirtieth.

This game uses three-dimensional graphics.

Asuna is my best friend.