pain or suffering

痛い(いたい)	Pain

苦しい(くるしい)	Suffering which is caused BY pain. i.e. ‘I got the flu. My throat is 痛い、 so talking or swallowing is 苦しい’

悲しむ(かなしむ)	Emotional suffering

苦しむ(くるしむ)	Physical suffering.