From Greek 'galaxías' (milky), from 'gála' (milk) — the ancient Greeks saw the band of stars and called it the 'milky circle'. The PIE root *ǵlákts (milk) also gave Latin 'lac' → lactose, latte, and even lettuce (named for its milky sap). Galaxy and lactose are etymological cousins.
A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction; specifically, the Milky Way.
From Late Latin 'galaxias', from Greek 'galaxías (kýklos)' (γαλαξίας κύκλος), meaning 'milky (circle)'. Derived from 'gála' (γάλα), meaning 'milk'. The ancient Greeks saw the band of light across the night sky and called it the 'milky circle' — the same metaphor used by the Romans, who called it 'via lactea' (milky way). The Greek myth attributed it to Hera's breast milk spraying across the sky when the infant Heracles was pulled from her breast. Key
The words 'galaxy' and 'lactose' are cousins — both descend from PIE *ǵlákts (milk). Greek kept the 'g' onset (gála → galaxy), while Latin shifted it to 'l' (lac → lactose, latte). Even 'lettuce' is related — Latin 'lactuca' (lettuce) was named for the milky sap that oozes from its cut stems