As nouns the difference between rucksack and rucksacs
is that rucksack is a bag carried on the back or shoulder, supported by straps while rucksacs is plural of rucksac.
rucksack
English
Noun
(
en noun)
a bag carried on the back or shoulder, supported by straps
Synonyms
* back pack or backpack
* knapsack
* haversack
* packsack