supplemental vs supplementary

supplemental and supplementary both are adjectives.

Word	Noun	Adjective	Verb	Adverb
supplemental	No	Yes	No	No
supplementary	No	Yes	No	No

As adjectives, supplemental and supplementary are synonyms defined as:

supplemental and supplementary: added to complete or make up a deficiency

As adjectives, supplemental and supplementary are synonyms defined as:

Other synonyms of supplemental include auxiliary, subsidiary.

supplemental (adjective)	supplementary (adjective)
added to complete or make up a deficiency	added to complete or make up a deficiency
functioning in a supporting capacity	functioning in a supporting capacity