* Orbifold signature: 
* Coxeter notation (rectangular): [&infin;,2,&infin;] or [&infin;]×[&infin;]
* Coxeter notation (square): [4,1,4] or [1,4,4,1]
* Lattice: rectangular
* Point group: D
* The group pmm has reflections in two perpendicular directions, and four rotation centres of order two (180°) located at the intersections of the reflection axes.
;Examples of group pmm