silver dollar vs dollar

silver dollar and dollar both are nouns.

Word	Noun	Adjective	Verb	Adverb
silver dollar	Yes	No	No	No
dollar	Yes	No	No	No

As nouns, dollar is a hypernym of silver dollar; that is, dollar is a word with a broader meaning than silver dollar:

silver dollar (noun)	dollar (noun)
southeastern European plant cultivated for its fragrant purplish flowers and round flat papery silver-white seedpods that are used for indoor decoration	a symbol of commercialism or greed
a dollar made of silver	a piece of paper money worth one dollar
	a United States coin worth one dollar
	the basic monetary unit in many countries; equal to 100 cents