1cir·cu·lar 
/ˈsɚkjəlɚ/ adjective
/ˈsɚkjəlɚ/ adjective 1 [more circular; most circular] : shaped like a circle or part of a circle
▪ a circular [=round] table ▪ They have a circular driveway. [=their driveway is curved like part of a circle] ▪ That planet has a more circular orbit than our planet does. 2 : moving or going around in a circle
▪ circular motion ▪ A circular [=spiral] staircase leads up to the loft. 3 [more circular; most circular] : incorrectly using a statement that may not be true to prove an idea or thought that would be false if the original statement was not true
▪ He used circular logic/reasoning/thinking. ▪ a circular argument/explanation
▪ a circular [=round] table ▪ They have a circular driveway. [=their driveway is curved like part of a circle] ▪ That planet has a more circular orbit than our planet does.
▪ circular motion ▪ A circular [=spiral] staircase leads up to the loft.
▪ He used circular logic/reasoning/thinking. ▪ a circular argument/explanation
— cir·cu·lar·i·ty /ˌsɚkjəˈlerəti/ noun [noncount]
▪ the circularity of her argument
/ˌsɚkjəˈlerəti/ noun [noncount] ▪ the circularity of her argument
