once

/wʌns/
adverb
  1. One time only.
    • Please read the instructions once before starting.
    • She called his name once, but he didn't hear her.
    • I have only been to Paris once.
  2. At some time in the past; formerly.
    • He once lived in a small village in the mountains.
    • This old building was once a school.
    • Once, people thought the Earth was flat.
  3. As soon as; when.
    • Once the rain stops, we will go for a walk.
    • Once you finish your homework, you can watch TV.
    • Once she arrives, the meeting can begin.
Antonyms
noun
  1. A single occasion or instance.
    • Just this once, you can stay up late.
    • He decided to give it one more try, just this once.
    • For once, I agree with you completely.