clockwise顺时针
coefficient系数
column列，圆柱
common denominator公分母
common difference等差数列的公差
common divisor(factor)共因子;公约数
common ratio等比数列的公比
common multiple公倍数
complement余角
complementary angle余角
complete circle全圆
complete quadratic (equation)全二次方程
complex fraction繁分数