n.

1. 循环，环流；运行[U][S1]
   We observed the circulation of blood in frogs.

   我们观察了青蛙的血液循环。

2. （货币、消息等的）流通，传播[U]
   Many forged notes are in circulation.

   许多假钞在流通。

3. （报刊等的）发行量，销售量[S]
   This paper has a circulation of more than a million.

   这一报纸的发行量达一百多万份。

4. 通货，货币[U]

n.

1. movement to and fro or around something.
   ▸the continuous motion by which blood travels through the body.
2. the public availability or knowledge of something:
   his music has achieved wide circulation.
3. the number of copies sold of a newspaper or magazine.