【问】 at a time与at one time有何区别?

【答】 at a time的意思是：“一次”、“一下子”：

1. You can borrow only two books at a time.

(你)一次只能借两本书。

2. He ran up the steps two at a time.

他一步两个梯级地往上跑。

3. Here are five points that help me learn——and remember——whole families of words ata time.

这里有五点要领可帮助我一下子学到——并记住——词的整个词族。

at one time的意思是：“一度”、“过去曾经”、“过去有个时期”、“同时”：

1. Most of the games probably had some religious meaning at one time，though many laterlost it. (TOEFL)

这些游戏大部分曾有过某些宗教含义，不过以后许多游戏就没有此种含义了。

2. No bank keeps enough cash to pay all its depositors in full at one time. (TOEFL)

没有一家银行拥有足够的现金能够同时支付所有储户的全部存款。

3. The technique at one time was arcane in the minds of most chemists.

这种技术在大多数化学家心目中曾一度是神秘的。