tryout vs trial balloon

tryout and trial balloon both are nouns.

Word	Noun	Adjective	Verb	Adverb
tryout	Yes	No	No	No
trial balloon	Yes	No	No	No

As nouns, trial balloon is a hyponym of tryout; that is, trial balloon is a word with a more specific, narrower meaning than tryout:

Other hyponyms of tryout include field test, field trial, alpha test, beta test, road test.

tryout (noun)	trial balloon (noun)
a test of the suitability of a performer	a balloon sent up to test air currents
trying something to find out about it	a test of public opinion