taxation vs single tax

taxation and single tax both are nouns.

Word	Noun	Adjective	Verb	Adverb
taxation	Yes	No	No	No
single tax	Yes	No	No	No

As nouns, single tax is a hyponym of taxation; that is, single tax is a word with a more specific, narrower meaning than taxation:

taxation: charge against a citizen's person or property or activity for the support of government
single tax: a system of taxation in which a tax is levied on a single commodity (usually land)

taxation (noun)	single tax (noun)
the imposition of taxes; the practice of the government in levying taxes on the subjects of a state	a system of taxation in which a tax is levied on a single commodity (usually land)
charge against a citizen's person or property or activity for the support of government
government income due to taxation