plural of math circle

(education) An informal space where people study and discuss mathematics, often involving games, hands-on activities, or competition.

(informal, humorous) Very difficult. / (informal, humorous) Very hard (in the sense of physical rigidity).

(colloquial) Relating to mathematics, typically connotating that the mathematics referred to is difficult.

(informal) The terminology of mathematics

A system that translates mathematical expressions (on a website for example) into spoken English for the benefit of blind people