adoucir

(of foods, flavors, scents, etc.) to sweeten; (of any unpleasant thing) to make (more) agreeable, pleasant, mild, delicate, etc.; (of something physically rough or coarse) to soften, to smooth; (of water) to soften; to soften, to make more delicate; (of colors, as in visual arts like painting) to lighten, to brighten

“La sauce est trop salée ; je vais l'adoucir un peu.” — The sauce is too salty; I'll sweeten it a bit.

Inherited from Old French adoucir, adolcir, from dolz, douz (“sweet”), from Latin dulcis (“sweet”). By surface analysis, a- + doux + -ir.