I have been to France once.

He finished all his work all at once.

The Zero was the main fighter of the Japanese Navy.

Reiji is my best friend.

A zero vector is a vector where all elements are zero.

This game is considered a zero-sum game.

This book, which is missing a large proportion of its scrolls, is a 'zero book'.

How is the longitude of the Earth determined?

He swore never to repeat that mistake twice.

He goes to the gym twice a day.