Triangle: prominent jaw, which is wider than the cheekbones
A triangular face has a prominent jaw that is wider than the cheekbones.
Men with this shape are better off clean-shaven and with medium-length hair.
Square: angular and prominent
Square faces have lots of sharp angles and, often, a masculine look.
They're similar to round faces in that they're best softened with a cut that's taller on the top. But square-faced men also have the option of going for a really short haircut that will balance out with their naturally round head.
Round: face is equal in length and width
Round faces could use some definition to make them appear longer.
Because of that, you may consider a cut that is shorter on the sides and taller on the top, which would give a round face balance.
Diamond: strong jaw and angular cheek bones
The best-case scenario here is to pair a beard with a fringed haircut like a faux hawk or textured crop.