Japanese phrase
___に一度です。 ___ ni ichi do de su
Meaning
Once every ___.
When to use it
States that something happens once during each time period. It gives a simple frequency without adding detail.
Example dialogue
オリンピックは何年に一度ですか？ o ri n pi kku wa nan nen ni ichi do de su ka
How often are the Olympics held?
四年に一度です。 yon nen ni ichi do de su
They are held once every four years.