I'm working on a problem on the braid monodromy of complex lines arrangements in $\mathbb{C}^{2}.$ I have the following question. It's just a simple definition. However, I didn't find anywhere.
Let $G$ be a group and let $\langle S\mid R\rangle$ be a presentation of $G.$ What does it mean that such presentation is minimal?
Thank you very much for everyone will answer and kind regards.