Solstice, equinox

On this page

• General information
• Origin of “solstice”
• Origin of “equinox”
• Capitalization
• Plural forms

General information

The words solstice and equinox refer to the astronomical events that mark the change of seasons: the winter solstice, the spring equinox, the summer solstice and the autumnal equinox.

Origin of “solstice”

The word solstice comes from the Latin words sol (sun) and stitium (standstill). At the solstice, the sun appears to “stand still” because the position of the sunrise on the horizon changes very little for a few days.

The winter solstice is the shortest day of the year, and in the northern hemisphere, it occurs around December 22. The summer solstice is the longest day of the year, and north of the equator, it occurs around June 21.

Origin of “equinox”

The word equinox comes from the Latin words aequus (equal) and nox (night). At the equinox, day and night are equal in length.

In the northern hemisphere, the spring equinox (also known as the vernal equinox) occurs around March 21 and the autumnal equinox occurs around September 23.

Capitalization

The words solstice and equinox are not capitalized.

• Festivals are held around the world to celebrate the summer solstice.
• Many cultures have built structures to align with the sun on the spring equinox.

Plural forms

The plural form of solstice is solstices; the plural form of equinox is equinoxes.

• At the solstices, the sun is farthest away from the equator.
• At the equinoxes, the sun is directly above the equator.