arduous
difficult and demanding
Roots
- -ous / -ious: full of or marked by a quality
- ardu: high, steep, difficult, or hard to climb
Arduous has a steep hill inside it: the task feels hard because it keeps climbing.
The scholarship application was arduous: essays, transcripts, interviews, and one more form after every form.
The older image behind arduous is height or steepness. That matters because arduous does not just mean hard. It means hard like a climb that keeps asking for more breath.
A hard task is one obstacle; an arduous task is the long slope that tests your endurance.