The central bank determines how much money is in circulation at a time.

中央银行决定有多少资金在流通。

According to the U.S. Federal Reserve, about $1.53 trillion worth of U.S. bills are in circulation right now.

根据美国联邦储备委员会的数据，目前流通的美国票据价值约为 1.53 万亿美元。

The bald eagle also appears, more importantly, on billions of one dollar bills that are in circulation or use.

更重要的是，白头鹰还出现在流通或使用的数十亿张一美元钞票上。

To give examples, we may use words like these: Old coins, especially ones that have never been in circulation, can have great value.

用来举例，我们可以诸如此类的词语：古老的钱币，尤其是那些从来没有在市场上流通的，可以有很大的价值。

11.8 ). Similarly, it is difficult to see how there could be any circulation of the blood in a two-dimensional creature.

11.8）。同样，很难看出二维生物体内怎么会有血液循环。

Metal was first coined into cash between 700 and 600 BC by the Lydians, and banknotes have been in circulation since their first use in China around 1000 AD. These days, though, habits have changed.

公元前 700 至 600 年， 吕底亚人首次将金属铸成现金，纸币自公元 1000 年左右首次在中国使用以来一直在流通。 然而，这些天来，习惯已经改变了。

As they report in PLOS ONE, their conclusion, from the random pattern of the scratches on it, was that this was an object which had indeed been in circulation, rather than something decked up to look worn by a forger.

正如他们在 PLOS ONE 中报告的那样，他们从上面随机划痕的图案得出的结论是， 这是一件确实流通过的物品， 而不是装扮成伪造者佩戴过的东西。