Supplementary is a related term of superfluous.
As adjectives the difference between supplementary and superfluous
is that supplementary
is additional; added to supply what is wanted while superfluous
is in excess of what is required or sufficient.
Additional; added to supply what is wanted.
In excess of what is required or sufficient.
- With a full rain suit, carrying an umbrella may be superfluous .
* excessive, extraneous, extra, pleonastic, supernumerary, surplus, unnecessary, extravagant