PREP
(置于某個年份之前，表示不確定)大約，大概
Circa is used in front of a particular year to say that this is the approximate date when something happened or was made.
例句
The story tells of a runaway slave girl in Louisiana, circa 1850.
故事大約發生在1850年，講的是路易斯安那州一個逃跑的年輕女奴。