indicator vs test paper

indicator and test paper both are nouns.

Word	Noun	Adjective	Verb	Adverb
indicator	Yes	No	No	No
test paper	Yes	No	No	No

As nouns, test paper is a hyponym of indicator; that is, test paper is a word with a more specific, narrower meaning than indicator:

indicator (noun)	test paper (noun)
a device for showing the operating condition of some system	paper impregnated with an indicator for use in chemical tests
a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time	a written examination
a signal for attracting attention
(chemistry) a substance that changes color to indicate the presence of some ion or substance; can be used to indicate the completion of a chemical reaction or (in medicine) to test for a particular reaction