In the next step of the lunar cycle, the moon appears only halfway illuminated. Though it's commonly called a half moon because of its shape, the correct term "quarter moon" refers to its cycle — one-quarter of the way around the Earth. Towards the beginning of the cycle, the phase is called "first quarter" and towards the end, it's called "third" or "last" quarter. The first quarter moon occurs one week after the new moon. The last quarter moon comes about three weeks after the new moon.