Hello Belinda, "sweetheart ,daRling, babe, baby , hun .etc..... those are affectionate ways used to address girlfriends, boyfriends, wives, husbands and all members of an intimate relationship between both genders. As for 'dear' it could be used affectionately as well , but also in a formal way at the beginning of a letter followed by the name of the person you are writing to ( whether male of female ) as in : Dear Belinda, ......... Other words you can use to express affection, love or liking : treasure, angel, sweetie , dearest , love....

babe and baby is almost always a boyfriend/ girlfriend thing all the rest of the terms can be either boyfriend/girlfriend or just a sweet old lady.