Learn how to say Supplemental correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word supplement:
something added, esp. to make up for a lack or deficiency
a section added to a book or the like to give additional information, correct errors in the body of the work, etc.
(US) a separate section containing feature stories, comic strips, or the like, issued with a newspaper
the amount to be added to a given angle or arc to make 180° or a semicircle
to provide a supplement to; add to, esp. so as to make up for a lack or deficiency