4. what word describes the position in the moon's elliptical orbit when it is closest to earth?

Perigee is the word that describes the position in the moon's elliptical orbit when it is closes to Earth. The term that is quite its opposite is apogee. Both perigee and apogee happen once a month, and the time period it takes the Moon to go through these phases, from perigee to apogee, is known as anomalistic month, which lasts for about 27 days.