arduous

US /ˈɑːr.dʒu.əs/
UK /ˈɑːr.dʒu.əs/
"arduous" picture
1.

ardu, difficile, pénible

involving or requiring strenuous effort; difficult and tiring

:
The climb up the mountain was long and arduous.
L'ascension de la montagne fut longue et ardue.
Learning a new language can be an arduous process.
Apprendre une nouvelle langue peut être un processus ardu.