knapsack vs backpack

knapsack and backpack both are nouns.

Word	Noun	Adjective	Verb	Adverb
knapsack	Yes	No	No	No
backpack	Yes	No	Yes	No

As nouns, knapsack and backpack are synonyms defined as:

knapsack and backpack: a bag carried by a strap on your back or shoulder

Other synonyms of knapsack include back pack, haversack, packsack, rucksack.

knapsack (noun)	backpack (noun)
a bag carried by a strap on your back or shoulder	a bag carried by a strap on your back or shoulder

knapsack (verb)	backpack (verb)
	hike with a backpack