Caption: A cartoon of main types of galaxies of the Hubble sequence (of galaxy types) which is the most usual/traditional galaxy classification scheme.

The 3 main types are spiral galaxies (which have galaxy disks and spiral arms), elliptical galaxies (which are just swarm of stars with relatively random orbital orientations), and irregulars (which, oddly enough, are irregular in structure).

The spiral galaxies are divided into unbarred spiral galaxies (which have NO galactic bars in their galactic bulges), barred spirals (which have galactic bars in their galactic bulges), and intermediate spiral galaxies (which are in between the other two kinds of spiral galaxies). In fact, the 3 subtypes are just ideal cases along of continuum from zero galactic bar to large galactic bar.

If one says spiral galaxies without qualification one can either mean (unbarred) spirals, or (unbarred) spirals and barred spirals. Context must decide the meaning.

Actually, galaxies with galactic bars are best since you can get a drink.

Credit/Permission: © David Jeffery, 2005 / Own work.
Image link: Itself.
Local file: local link: galaxy_types_main.html.
File: Galaxies file: galaxy_types_main.html.