stock symbol vs symbol

stock symbol and symbol both are nouns.

Word	Noun	Adjective	Verb	Adverb
stock symbol	Yes	No	No	No
symbol	Yes	No	No	No

As nouns, symbol is a hypernym of stock symbol; that is, symbol is a word with a broader meaning than stock symbol:

stock symbol: the letters used to identify listed companies on the securities exchanges where they are traded
symbol: an arbitrary sign (written or printed) that has acquired a conventional significance

stock symbol (noun)	symbol (noun)
the letters used to identify listed companies on the securities exchanges where they are traded	something visible that by association or convention represents something else that is invisible
	an arbitrary sign (written or printed) that has acquired a conventional significance