Refers broadly to someone who is ill, whether at home or under care. Compared with 患者, it emphasizes the person's being sick rather than their role as a medical patient; the English gloss 'invalid' is old-fashioned and means someone incapacitated by illness.
There is a sick person at home, so I will go home early today.
You must not force a sick person to work.
My mother is nursing the sick person.
I visited the sick person together with a friend.
Every winter someone in this house falls ill.
I hated being treated like an invalid even though I felt fine.
nurse; caregiver
seriously ill person; person with a serious illness