arduous
US /ˈɑːr.dʒu.əs/
UK /ˈɑːr.dʒu.əs/

1.
艰巨的, 费力的, 辛苦的
involving or requiring strenuous effort; difficult and tiring
:
•
The climb up the mountain was long and arduous.
爬山的过程漫长而艰巨。
•
Learning a new language can be an arduous process.
学习一门新语言可能是一个艰巨的过程。