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

1.
艱鉅的, 費力的, 辛苦的
involving or requiring strenuous effort; difficult and tiring
:
•
The climb up the mountain was long and arduous.
爬山的過程漫長而艱鉅。
•
Learning a new language can be an arduous process.
學習一門新語言可能是一個艱鉅的過程。