Sweetheart in Russian

The diminutive suffixes (-ышк-, -очк-, -ик) are a productive machine: almost any noun can be made small and dear, and couples invent private endearments constantly. The four above are the safe, universal core.

Register matters more than translation: солнышко from a partner is tender, from a stranger it is presumptuous. When unsure, admire with the adjective (милый, милая) rather than a noun; nouns claim closeness.