sportscaster vs announcer

sportscaster and announcer both are nouns.

Word	Noun	Adjective	Verb	Adverb
sportscaster	Yes	No	No	No
announcer	Yes	No	No	No

As nouns, announcer is a hypernym of sportscaster; that is, announcer is a word with a broader meaning than sportscaster:

sportscaster: an announcer who reads sports news or describes sporting events
announcer: reads news, commercials on radio or television

sportscaster (noun)	announcer (noun)
an announcer who reads sports news or describes sporting events	reads news, commercials on radio or television
	someone who proclaims a message publicly