arduous vs laborious

arduous and laborious both are adjectives.

Word	Noun	Adjective	Verb	Adverb
arduous	No	Yes	No	No
laborious	No	Yes	No	No

As adjectives, arduous and laborious are synonyms defined as:

arduous and laborious: characterized by effort to the point of exhaustion; especially physical effort

Other synonyms of arduous include backbreaking, grueling, gruelling, hard, heavy, operose, punishing, toilsome.

arduous (adjective)	laborious (adjective)
difficult to accomplish; demanding considerable mental effort and skill	characterized by effort to the point of exhaustion; especially physical effort
characterized by effort to the point of exhaustion; especially physical effort
taxing to the utmost; testing powers of endurance