To be considered similar, two polygons have corresponding sides that are equal. always never sometimes

To be considered similar, two polygons sometimes have corresponding sides that are equal.

"  Two figures are said to be similar if the ratio of each of the corresponding  sides of the two figures are equal "

Hence, if both the figures have sides of equal length then obviously the ratio of each of the corresponding sides is equal i.e. 1:1.

Also, the ratio may be same if the original figure is dilated by some scale factor.

This means that now in this case the corresponding sides are not equal.