Which undefinable geometric concept has no dimension

I believe it is 2-D because, it is the only dimension that has no depth so, you can only see it from one side.

Ifound this on google “a skewed (non-symmetric) distribution is a distribution in which there is no such mirror-imaging. a "skewed right" distribution is one in which the tail is on the right side. a "skewed left" distribution is one in which the tail is on the left side. the above histogram is for a distribution that is skewed right.” i hope this you for what your looking for