Is there a name for the power of the exponent of a $p$-group? So, if $\mathrm{exp}(G):=\max\lbrace o(g)|g\in G\rbrace=p^k$ for some $k\in\mathbb{N}$, is there a name for the $k$? Additionally, is there a name for the power $n$ of the order of a $p$-group with $|G|=p^n$ for some $n\in\mathbb{N}$?
I am new to $p$-groups and I was also wondering, if it is even "interesting" to consider special cases of $n$ and $k$, for example, if both are prime as well. I am using the books by "Groups of Prime Power Order" by Yakov Berkovich et al. to get a feeling for the topic and they do not (so far) talk much about these terms $n$ and $k$.
My interest arises from an application in statistical mechanics which "enforces" certain powers.