mathematical symbol vs graph

mathematical symbol and graph both are nouns.

Word	Noun	Adjective	Verb	Adverb
mathematical symbol	Yes	No	No	No
graph	Yes	No	Yes	No

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

mathematical symbol: a character that is used to indicates a mathematical relation or operation
graph: a written symbol that is used to represent speech

Other hypernyms of mathematical symbol include character, grapheme, graphic symbol.

mathematical symbol (noun)	graph (noun)
a character that is used to indicates a mathematical relation or operation	a visual representation of the relations between certain quantities, represented as points, plotted with reference to a set of axes
	a visual display of information
	a written symbol that is used to represent speech

mathematical symbol (verb)	graph (verb)
	represent by means of a graph
	plot upon a graph