The moon is the object that you can often see in the sky at night. It goes around the earth once every four weeks, and as it does so its appearance changes from a circle to part of a circle.
双语例句
例： the first man on the moon.
登月第一人。
例： the light of a full moon.
满月的光芒。
例： The moon orbits the earth approximately once each month.
月球大概每月环绕地球旋转一圈。