adverb
- one time only
- at some time in the past; formerly
- at some time in the future
conjunction
- as soon as; when
Examples
- I've only been to Paris once.
- She called once but didn't leave a message.
- This building was once a factory.
- He was once the most popular singer in the country.
- Once you finish your homework, you can watch TV.
- Once we arrive, we'll call you.
- Try it once more before giving up.