A galaxy is a large astronomical structure containing several billions of stars and other astronomical bodies, looking like a more or less regular spiral with a thick core and thinner edges.
The Milky Way is the galaxy where our Earth is located, it has about 200 billion stars.
The known universe contains billions of galaxies.
(special) The galaxy : the galaxy we live in, the Milky Way (very often employed with the definite article).
Some science-fiction writers imagine that mankind will one day settle an empire throughout the galaxy.
