In mathematics, "sameness/similarity of forms" is defined for parts of a space. That is,
If, for parts A and B, such a 1-1 correspondence ("isomorphism") f can be constructed between the sets A and B as some condition is fulfilled, then A and B are said to be similar.
Condition of "isomophism f" in this example is :
If and only if vertices X and Y span a edge so do f(X) and f(Y).
For real objects A and B, the sameness or similarity of their forms could be computed by means
of their pictures. That is,
we introduce a space E,
identify A and B with E's parts A' and B', and
see if, between A' and B', such map as some condition is fulfilled can be constructed.
