sweetheart
Definitions
A person who is dearly loved, especially a romantic partner.
A person who is charming, kind, or generous.
A term of endearment used to address someone affectionately.
Examples
My grandmother is such a sweetheart that she bakes cookies for the entire neighborhood.
He whispered a soft endearment to his sweetheart before boarding the train.
Don't worry about the mistake, sweetheart; everyone learns from their errors eventually.