The definition of supplementary is something that is added on, or that completes something.
An example of supplementary is a workbook that comes with a regular textbook.
Supplying what is lacking; additional.
Supplementary Sentence Examples
Helen Keller's letters are important, not only as a supplementary story of her life, but as a demonstration of her growth in thought and expression--the growth which in itself has made her distinguished.
Supplementary to the preceding was the Nova litteraria Germaniae collecta Hamburgi (1703-1709), which from 1707 widened its field of view to the whole of Europe.
20 and the supplementary treaty Aug.
Historical inscriptions, royal charters and rescripts, despatches, private letters and the general literature afford welcome supplementary information.
Similarly in Europe they are often the property of the International Sleeping Car Company (Compagnie Internationale des Wagons-Lits), and the supplementary fares required from those who travel in them add materially to the cost of a journey.