Could someone point me to a definition of "odd order"? The definition of group order I found here seems to refer to a group as a set of numbers. The context that I'm reading about 'odd order' is: "$p\ \alpha\ d_{eh_1}E(t)$; it is initially linear in $E(t)$ and thus of odd order with respect to the driving field sign".
Then later it mentions $d^2_{eh_1}E(t)^2$ as also being of odd order. Could someone clarify why this is the case?