symphony vs orchestra

symphony and orchestra both are nouns.

Word	Noun	Adjective	Verb	Adverb
symphony	Yes	No	No	No
orchestra	Yes	No	No	No

As nouns, orchestra is a hypernym of symphony; that is, orchestra is a word with a broader meaning than symphony:

symphony: a large orchestra; can perform symphonies
orchestra: a musical organization consisting of a group of instrumentalists including string players

symphony (noun)	orchestra (noun)
a long and complex sonata for symphony orchestra	seating on the main floor in a theater
a large orchestra; can perform symphonies	a musical organization consisting of a group of instrumentalists including string players