Answer: Days and nights are equal in length everywhere.
Explanation:
Equinox means equal night. There are two equinox - vernal equinox and autumnal equinox. When the sun crosses celestial equator, the sun rays fall directly over equator at noon. Thus, there is equal length of day and night in the two hemisphere. It occurs around March 22 and September 22.
The similarity is that they both are types of bonds in molecules. Ionic bonds are between a metal and a nonmetal. Covalent bonds are between two nonmetals.