[bnegreve]

> in "pixels wide" the word "wide" acts as a square root operator on the area and means "pixels^(-2)"

Did you meant "pixels^(1/2)"? I'm not sure what kind of units pixels^(-2) would be.

[nayuki]

pixel^(-2) is "per squared pixel". Analogously, 1 pascal = 1 newton / 1 metre^2. (Pressure is force per squared length.)