A nurse is a trained healthcare worker who takes care of sick people. To nurse is to take care of, like if you nurse a baby bird back to health.
To become a nurse, you have to go to college and study subjects like anatomy and nutrition. Some nurses assist doctors and perform tasks like bathing patients, taking blood samples, or giving medication. When you use the word nurse as a verb, it means "care for," and also "breastfeed a baby." The Latin root, nutrire, means "to nourish." To nurse a drink is to drink it slowly, and to nurse an idea is to mull it over.