0 one time -- مَرَّة واحِدة
1 in the past, but not now -- في الماضي
This house once belonged to my grandfather.
2 immediately -- حالاً
I knew at once that I would like it here.
3 one more time -- مَرّة أُخْرى
If you say that once more, I’m going to leave.
4 used at the beginning of a children’s story to mean that something happened a long time ago -- كان يا مَكان/ يُحْكي أنَّه كان… في سالِف الزَّمان…
5 again -- مَرّة أُخرى
I’ll explain it once again.