galaxy

A Google search leads to this as the first definition of galaxy:

Web definitions for galaxy

A system of about 100 billion stars. Our Sun is a member of the Milky Way Galaxy, which is sometimes just designated by capitalization: Galaxy. There are billions of galaxies in the observable universe. Exactly when and how galaxies formed in the Universe is a topic of current astronomical research.

antwrp.gsfc.nasa.gov/apod/lib/glossary.html