One Time
Once
noun
One times is one time. How many times? Just one.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. Take note that 一 is shortened (as it often is) to いっ.
一回だけ
only once
一回ずつ
once each, one at a time
一回きり
only once
もう一回、言ってください。
Please say it once more.
平日は一日に一回シャワーをあびます。
On weekdays, I shower once a day.
毎月、一回はラーメンをたべに町へ出かけます。
Every month, I go to town for ramen at least once.