If you plant a seed, water it daily and give it lots of light, you nurture it until it is ready to be transplanted outside. When you nurture a person or thing, you care for it and help it to grow.
After a fight with your friend, you may have to nurture the relationship a little until you're close again. Use the phrase "nature versus nurture" to help you remember the word. Nature is a baby just out of the womb. Nurture is how that baby is raised or taken care of. Once the child is older, you may wonder if its love of reading is nature or nurture — is it natural born or is it because you read to the baby every night.