supplementary

/ˌsʌpləˈmɛntəri/
adjective
  1. Added to something to improve or complete it; extra.
    • The report includes supplementary information about the project.
    • The teacher gave us a supplementary worksheet for practice.
    • She earns supplementary income from her online store.
  2. In geometry, describing two angles that add up to 180 degrees.
    • If one angle is 110 degrees, its supplementary angle is 70 degrees.
    • Supplementary angles together form a straight line.
    • The students learned to identify supplementary angles in class.