Definition of "equinox" []

• Either of two points on the celestial sphere at which the ecliptic intersects the celestial equator. (noun)
• Either of the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal; the vernal equinox or the autumnal equinox. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The word equinox comes from the Latin words for "equal" and "night.""
• "Instead of Summer and Winter Solstice, it should be Periuma and Apuma, and without an axial tilt the term equinox is moot -- every day is equal amounts of day and night."
• "The Truth: The vernal equinox is one of two days each year when the length of day and night are the same (about 12 hours each)."