Mary Jane vs ganja

Mary Jane and ganja both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mary Jane	Yes	No	No	No
ganja	Yes	No	No	No

As nouns, ganja is a hypernym of Mary Jane; that is, ganja is a word with a broader meaning than Mary Jane:

Mary Jane: street names for marijuana
ganja: the most commonly used illicit drug; considered a soft drug, it consists of the dried leaves of the hemp plant; smoked or chewed for euphoric effect

Other hypernyms of Mary Jane include cannabis, marihuana, marijuana.

Mary Jane (noun)	ganja (noun)
street names for marijuana	the most commonly used illicit drug; considered a soft drug, it consists of the dried leaves of the hemp plant; smoked or chewed for euphoric effect
	a strong-smelling plant whose dried leaves can be smoked for a pleasant effect or pain reduction