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difficult; hard; troublesome; complicated; serious (disease, problem, etc.)
impossible; unfeasible
fussy; particular; fastidious; hard to please; displeased
gloomy; glum; sullen; serious (look)
今回の試験の問題は難しい。
The questions on this exam are difficult.
予算不足で、海外進出は難しいと思う。
With insufficient budget, expanding overseas would be unfeasible, I think.
難しくても諦めたくないです。
Even if it's hard, I don't want to give up.