A situation for which each member of a set, such as angles of a triangle, can be paired with one and only one member of another set. - ? Angles paired with one another in a one-to-one correspondence between geometric figures. - ? Sides paired with one another in a one-to-one correspondence between figures. - ? If a one-to-one correspondence between the parts of two figures is such that the corresponding parts are equal, then the figures are congruent. - ? The angle formed by two sides of a triangle. - ? The side of a triangle that is formed by the common side of two angles. - ?