The circumference is the amount of length around the circle the diameter is the distance across the middle of the circle, first off you need the formulas which are to find the circumference of a circle use the formula C=2 * (pi) * r to find the diameter use the formula D=2 * (pi) and remember that the radius of a circle is the distance from the perimeter of the circle to the center of the circle (half the diameter) so half of 14 equals 7,so in close C= 2 * 3.14 * 7 = 43.96. Enjoy!=)