arduous
adj.describing a task that is very difficult and takes a lot of effort over a long time. It often makes you feel physically or mentally tired.
adj.requiring strenuous effort; difficult and tiring. Often used to describe physical journeys or complex mental processes that demand sustained energy.
“The hikers began their arduous climb up the mountain.”
“After an arduous three-year investigation, the committee finally released its report on the financial scandal.”
“The transition from a command economy to a market-based system proved to be an arduous process, fraught with social upheaval and unexpected economic setbacks.”
Typically used attributively before a noun or predicatively after a linking verb like 'be' or 'become'.
“Her husband, Yuk Yuk’s co-founder Mark Breslin, has needed to use a cane lately, and when there’s no nearby parking, just getting into a local business can be arduous, she said.”
“Although the country is beginning to turn to the long-term consequences of the disaster, emergency responders continue the arduous labour of digging through the rubble.”
From Latin arduus (“lofty, high, steep, hard to reach, difficult, laborious”), akin to Irish ard (“high”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.