是once:
adv. 一次曾经
conj. 一旦
n. 一次，一回
I have visited grandma once this week.
我这周去看过奶奶一次。
I met Miquela once， briefly.
我见过蜜凯拉一次，时间很短。
Just for once he arrived on time.
只有这一次他按时到了。
The water is fine once you're in!
你一旦下了水，就会觉得水里挺舒适。
I've only been there once.
我只去过那里一次。
