requiring significant effort or difficult

कठिन

English Usage: The journey through the mountains was arduous.

Hindi Usage: पहाड़ों के पार यात्रा कठिन थी।

an arduous task or effort

कठिन कार्य

English Usage: Completing the project was an arduous.

Hindi Usage: प्रोजेक्ट पूरा करना एक कठिन कार्य था।