Use the word darling for someone you love or care for deeply. Your sweet old grandmother probably calls you darling.
You can describe someone as being your darling, or address them that way: "I missed you so much while I was working on that fishing boat, darling!" Another way to use the word is for a generally lovable person: "Everyone adores Timmy, he's such a darling." The Old English root is deorling, a diminutive of deor, "dear."