arduous
adj.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.
From Latin arduus (“lofty, high, steep, hard to reach, difficult, laborious”), akin to Irish ard (“high”).
Typically used attributively before a noun or predicatively after a linking verb like 'be' or 'become'.