equinox
UK[ˈek.wɪ.nɒks]US[ˈiː.kwə.nɑːks]
n
Either of the two times in the year (around March 20 and September 22) when the sun crosses the celestial equator, making day and night of approximately equal length everywhere on earth.
Morpheme Breakdown
equi
nox
equi
equal
nox
night
Etymology
The word "equinox" is a direct borrowing from the Medieval Latin equinoxium, which itself is a combination of the classical Latin roots aequus (equal) and nox (night). The term was constructed to describe the specific astronomical moments when the duration of day and night are equal. This concept is built on the ancient observation of the sun's path, where "equal night" literally defines the event's most noticeable characteristic. The modern abstract meaning retains this precise, literal logic, referring to the two annual dates when this celestial equality occurs.
Analysis
Structure: equi (equal) + nox (night)
- equi: From Latin aequus (equal, level). A combining form meaning "equal."
- nox: From Latin nox (night). A root meaning "night."
Examples
The vernal equinox marks the beginning of spring in the Northern Hemisphere.
Many ancient cultures built monuments aligned with the sunrise on the equinox.
Day and night are nearly equal in length during an equinox.