Having the shape of a circle; round. Can also describe something that moves in a circle or returns to its starting point.
From Latin 'circularis' from 'circulus' meaning small circle, diminutive of 'circus' meaning ring or circle. The word entered English in the 14th century, initially describing geometric shapes before extending to logical arguments and movements.
Circular motion is fundamental to everything from planetary orbits to the electrons spinning around atomic nuclei. Interestingly, 'circular reasoning' uses the geometric metaphor to describe flawed logic that returns to its starting point without proving anything.
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