The perigee is the point in the orbit of an object circling the Earth when that object is closest to the Earth. The best time to observe the moon is when the moon reaches its perigee.
The Greek ancestor of the word perigee was originally used by Ptolemy, a Roman scientist and astrologer who lived almost 2,000 years ago. The opposite of perigee is apogee. A perigee is measured from the center of the earth to the center of the orbiting object. When the moon is at its perigee, it can appear up to 14 percent larger than when it is at its apogee, but you probably can't tell the difference with the naked eye.