# Terminology for dihedral groups

What notation is most common for the dihedral group of order $2n$? I'm talking about the group of symmetries of a regular $n$-gon. I know that some books call this group $D_n$, and some books call it $D_{2n}$. There are probably other notations as well.

What notation, if any, is considered more standard? Is there a difference (as there often is) between the US and Europe?

I know that, if I'm writing anything about such a group, I will need to define my notation in context; I'm not asking so that I can be lazy and just use one notation without specifying what it means. I mention this only to prevent people lecturing me about defining my terms in mathematical writing - you would be preaching to the choir. I just wonder what, if anything, people view as "standard".

• I think you'll have to count votes. I've always called it $D_n$. – Ethan Bolker Dec 10 '17 at 18:25