Corresponding sides and corresponding angles

In geometry, the tests for congruence and similarity involve comparing corresponding sides of polygons. In these tests, each side in one polygon is paired with a side in the second polygon, taking care to preserve the order of adjacency.

For example, if one polygon has sequential sides a, b, c, d, and e and the other has sequential sides v, w, x, y, and z, and if b and w are corresponding sides, then side a (adjacent to b) must correspond to either v or x (both adjacent to w). If a and v correspond to each other, then c corresponds to x, d corresponds to y, and e corresponds to z; hence the i element of the sequence abcde corresponds to the i element of the sequence vwxyz for i = 1, 2, 3, 4, 5. On the other hand, if in addition to b corresponding to w we have c corresponding to v, then the i element of abcde corresponds to the i element of the reverse sequence xwvzy.