arduous vs strenuous

arduous and strenuous both are adjectives.

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

As adjectives, arduous and strenuous are synonyms defined as:

arduous and strenuous: taxing to the utmost; testing powers of endurance

Other synonyms of arduous include straining.

arduous (adjective)	strenuous (adjective)
difficult to accomplish; demanding considerable mental effort and skill	taxing to the utmost; testing powers of endurance
characterized by effort to the point of exhaustion; especially physical effort	characterized by or performed with much energy or force
taxing to the utmost; testing powers of endurance