Synonyms of arduous in English:

arduous


See US English definition of arduous

See UK English definition of arduous

See Spanish definition of arduo

adjective

1‘she was now faced with an arduous journey into a remote country’

SYNONYMS
onerous, taxing, difficult, hard, heavy, laborious, burdensome, strenuous, vigorous, back-breaking, stiff, uphill, relentless, Herculean
demanding, trying, tough, challenging, formidable, exacting
exhausting, wearying, fatiguing, tiring, punishing, gruelling, grinding
intolerable, unbearable, murderous, harrowing
informal killing, no picnic
British informal knackering
archaic toilsome
rare exigent
ANTONYMS

easy, effortless