← Back to arduous
Full Level C2 →
arduous Etymology Atlas
Needing or using up much energy; testing powers of endurance., burning; ardent Pro
Word
Root
Affix
Tap any word to open its Atlas. Pinch to zoom, drag to pan.
arduous is a Level C2 word — Pro only
Pro unlocks the Etymology Atlas for levels A2–C2 — plus FSRS-5 spaced repetition, mastery tracking, and the activity dashboard.