14 cm is the circumference or distance around the bulb. Dividing 14 by 2.54 (the number of centimeters per inch gives us 5.5 inches around. Then, dividing 5.5 inches by 3.1416 will give the diameter, something that's meaningfull. In this case that would be 1.75 inches across.
14 cm is considered optimum size for lily growers and gardeners alike for many reasons.
Edit added: The US Fifty Cent Coin is very near 14 cm or 1.75 inches.
