One of my students was trying to use the "perimeter" of one of the square faces from a square cuboid to calculate other measurements. From my understanding, perimeter is only defined for polygons. However, it seems to me that the idea of the "perimeter" of each face can be useful and there must have a way of expressing this in proper mathematical terms. As a note, this inquiry is for my own curiosity and the student was included as to show from where these thoughts came.
I haven't focused too much into higher areas of geometry and topology, so even the terminology is slightly confusing. I have worked with projections in vector calculus, as well as affine transformations in linear algebra, and parameterization in multiple courses. I suspect I have to somehow "squish" the cuboid to work with it in 2-dimensional spaces in order to apply the analysis and algebraic operations I wish. What is the formal terminology for doing this, and how do I write it?