# Need help with notation. Is this lower dot an operation?

I'm working through Introduction to Lie Algebras and Representation Theory by Humphreys, and I came across this notation $L.v$ as you can see in the picture. I cannot find where it's first introduced, or maybe it's assumed known.

• The elements of $L$ are matrices, if you want. So $L.v=\{Av\mid A\in L\}$. – Dietrich Burde Jan 15 '18 at 19:17