The word "galaxy" is used to describe a group of stars and other objects that share a gravitational pull and exist as a coherent system separate from other, similar groups. These systems are often isolated from other star groupings by vast empty areas of space.
"Galaxy" entered the English language from the Old French "galaxie," from the Latin "galaxias." The original word comes from the Ancient Greek "galaxas kklos," literally meaning "Milky Way," with " gla," the word for milk, describing its appearance in the sky. In the 14th century, the word "galaxy" was used to refer to the Milky Way specifically.