Advanced dynamics

I think anyone who is going to use Musescore knows ppp, pp, p, mp, mf, f, ff, fff, and maybe some of the additional dynamic marks in the advanced menu. Most of the advanced menu marks are explained in Wikipedia or elsewhere. But these one-letter marks are a mystery to me, in spite of searching: m, r, s, z, n. I couldn't figure out what they do even with experimentation.

In addition to answers here, it might be nice to add them to the documentation -- and maybe also to Wikipedia article on dynamics, if they're standard but obscure.