young moon

plural young moons

1. The phase of the moon when it is waxing, especially before quarter moon.
2. The moon when it is waxing.

   John E. Westfall (2000), Atlas of the Lunar Terminator, page 61: “The young Moon is best observed shortly after a springtime sunset, as is the case here.”

   2 more examples

   Fred Schaaf (1983), Wonders of the Sky: Observing Rainbows, Comets, Eclipses, the Stars and Other Phenomena, page 70: “Thus you can know that it would be impossible to see a young moon at sunset if new moon had occurred just a few hours earlier.”

   Chet Raymo (2005), The Soul of the Night: An Astronomic Pilgrimage, page 26: “There is a legend that Johannes Kepler, the Renaissance astronomer, once saw the old moon one morning and the young moon on the evening of the same day, but the story is hardly credible.”