/ ˈsɜːkjələ(r); NAmE ˈsɜːrk-/ adjective , noun
■ adjective
1.
shaped like a circle; round :
a circular building
2.
moving around in a circle :
a circular tour of the city
3.
( of an argument or a theory ) using an idea or a statement to prove sth which is then used to prove the idea or statement at the beginning
4.
( of a letter ) sent to a large number of people
► cir·cu·lar·ity / ˌsɜːkjəˈlærəti; NAmE ˌsɜːrk-/ noun [ U ]:
There is a dangerous circularity about this argument.
■ noun
a printed letter, notice or advertisement that is sent to a large number of people at the same time
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WORD ORIGIN
late Middle English : from Old French circulier , from late Latin circularis , from Latin circulus small ring, diminutive of circus ring.