Triangles are at least a third of geometry (tri = three . . . a little geometry humor). But, seriously, the sides and angles of triangles may have all sorts of relationships to each other, and the following list shows the abbreviations that indicate these relationships:

  • SSS: Side-side-side congruency

  • SAS: Side-angle-side congruency

  • ASA: Angle-side-angle congruency

  • AAS: Angle-angle-side congruency

  • HL(R): Hypotenuse-leg-(right angle) congruency

  • AA: Angle-angle similarity

  • SSS~: Side-side-side similarity

  • SAS~: Side-angle-side similarity

  • CPCTC: Corresponding parts of congruent triangles are congruent

  • CSSTP: Corresponding sides of similar triangles are proportional