# What does Sa and Sab mean for spiral galaxies?

I have learned that the notation to classify spiral galaxies in the De Vaucouleurs system goes like "SA for spirals without bar, SB for spirals with bar and SAB for intermediate spirals". But in some places I've seen galaxies classified as Sa or Sab for example. What it means and what is the difference between a Sa and a Sab spiral?

• Ok, reading this, it seems that Sa and Sab are just abbreviations for the usual SA, SB and SAB classification of the De Vaucouleurs system + "a" and "ab" at the end, denoting intermediate stages. Also, it says that "Sa galaxies tend to have significant bulges, and tightly-wrapped and relatively smooth spiral arms. Sab galaxies are similar to Sa galaxies, but show more obvious resolution of the arms." – Elismar Lösch Jan 31 at 23:50
• de Vaucouleurs SA = Hubble S. – Mike G Feb 1 at 1:24
• @ElismarLösch Sa and Sab are not abbreviations for SA and SAB (see my answer for details); the second part of your comment is correct. – Peter Erwin Feb 3 at 12:56