Definition
Refers to a single occasion or instance of something happening.
一次
I've been to London the once, but I can't remember when I last went.
我去過倫敦一次，但我不記得上次是什麼時候去的。
She's only eaten at that restaurant the once, and she said the food was average.
她只在那家餐廳吃過一次，她說食物很一般。
They have only met the once, but they decided to get married.
他們只見過一次，但他們決定結婚。