Other forms: sweetened, sweetening, sweetens
To sweeten is to make something taste sweeter or sound better. Sweeten the tea, sweeten the deal, sweeten the pill.
In cooking it is plain. Figuratively, to sweeten a deal is to add something to make it more attractive, and sweeten the pill means making bad news easier to take. Note sweetener, which means both the substance and, in business, an inducement — sometimes a euphemism for a bribe; and that sweeten displaced two French borrowings that did the same job.
1verbsweetenTo make something taste sweeter.
“She sweetened her tea with a spoonful of honey.”
2verbattractiveTo make an offer more attractive.
“To sweeten the deal, the company offered a free phone with the contract.”
sweeten is a making sweeter.
Sweet plus -en, the ending that makes verbs meaning to make more so. It pushed out the borrowed doucen, from the French for sweet.
Proto-Indo-European
*sweh₂d-
Middle English
swete
English
sweet
English, today
sweeten
Built from
From sweet + en. Eclipsed non-native doucen and endoucen, borrowed from adoucir and endoucir (“to sweeten”). sweet comes from Middle English swete. From Middle English soot, sweete, swete, swoote, from Old English swēte, swoete, swōt, swœ̄te (“sweet”), from Proto-West Germanic swōtī, from Proto-Germanic swōtuz (“sweet”), from Proto-Indo-European swéh₂dus (“sweet”), from sweh₂d- (“sweet”) + -us. 2
Etymology from Wiktionary, CC BY-SA