The moon is said to be in a waxing gibbous phase when it appears more than half-lighted but less that full – when it rises between noon and sunset – and when it sets in the wee hours after midnight. You’ll always see a waxing gibbous moon between a first quarter moon and full moon.
Any moon that appears more than half lighted but less than full – whether waxing or waning – is said to be a gibbous moon. The word gibbous comes from a root word that means hump-backed.
People often see a waxing gibbous moon in the afternoon, shortly after moonrise, while it’s ascending in the east as the sun is descending in the west. It’s easy to see a waxing gibbous moon in the daytime because, at this phase of the moon, a respectably large fraction of the moon’s dayside faces our way.
As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.
Bottom line: A waxing gibbous moon comes between first quarter moon and full moon. It appears more than half illuminated, but less than full. The next full moon – Harvest Moon for the northern hemisphere – will be September 24-25, 2018.
Check out EarthSky’s guide to the bright planets.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.