marijuana vs cannabis

marijuana and cannabis both are nouns.

Word	Noun	Adjective	Verb	Adverb
marijuana	Yes	No	No	No
cannabis	Yes	No	No	No

As nouns, marijuana and cannabis are synonyms defined as:

marijuana and cannabis: 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 synonyms of marijuana include ganja, marihuana.

As nouns, cannabis is a hypernym of marijuana; that is, cannabis is a word with a broader meaning than marijuana:

marijuana: a strong-smelling plant whose dried leaves can be smoked for a pleasant effect or pain reduction
cannabis: any plant of the genus Cannabis; a coarse bushy annual with palmate leaves and clusters of small green flowers; yields tough fibers and narcotic drugs

Other hypernyms of marijuana include hemp.

marijuana (noun)	cannabis (noun)
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	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	any plant of the genus Cannabis; a coarse bushy annual with palmate leaves and clusters of small green flowers; yields tough fibers and narcotic drugs