tax vs surtax

tax and surtax both are nouns.

Word	Noun	Adjective	Verb	Adverb
tax	Yes	No	Yes	No
surtax	Yes	No	Yes	No

As verbs, surtax is a hyponym of tax; that is, surtax is a word with a more specific, narrower meaning than tax:

Other hyponyms of tax include excise, tariff, overtax.

tax (noun)	surtax (noun)
charge against a citizen's person or property or activity for the support of government	an additional tax on certain kinds of income that has already been taxed

tax (verb)	surtax (verb)
make a charge against or accuse	levy an extra tax on
use to the limit
levy a tax on
set or determine the amount of (a payment such as a fine)