• adv. 一次；曾经
• conj. 一旦
• n. 一次，一回

来自one,一，-ce,副词后缀。

once

once: [12] Once originated as the genitive form of one (the genitive case was widely used in Old and Middle English for making adverbs out of nouns – other examples include always, needs, nowadays, and towards). To begin with, this was clearly indicated by its spelling – ones – but from about the start of the 16th century -es was gradually replaced by -ce (reflecting the fact that once retained a voiceless /s/ at its end, whereas in ones it had been voiced to /z/).
=> one

once (adv.)

c. 1200, anes, from ane "one" (see one ) + adverbial genitive. Replaced Old English æne. Spelling changed as pronunciation shifted from two syllables to one after c. 1300. Pronunciation change to "wuns" parallels that of one. As an emphatic, meaning "once and for all," it is attested from c. 1300, but this now is regarded as a Pennsylvania German dialect formation. Meaning "in a past time" (but not necessarily just one time) is from mid-13c.

Once upon a time as the beginning of a story is recorded from 1590s. At once originally (early 13c.) meant "simultaneously," later "in one company" (c. 1300), and preserved the sense of "one" in the word; the phrase typically appeared as one word, atones; the modern meaning "immediately" is attested from 1530s.

1. It had once been the home of a wealthy nobleman.

这里曾是一个有钱贵族的宅邸。

来自柯林斯例句

2. We tend to meet up for lunch once a week.

我们往往每周共进一次午餐。

来自柯林斯例句

3. He once told an interviewer that he didn't even like rock music.

他曾告诉一位采访者，他甚至都不喜欢摇滚乐。

来自柯林斯例句

4. Once wholesale prices are deregulated, consumer prices will also rise.

一旦批发价格放开，零售价格也会随之上涨。

来自柯林斯例句

5. He took off at once and headed back to the motel.

他立刻离开，回到汽车旅馆。

来自柯林斯例句