Verb

1. To make sweet to the taste; as, to sweeten tea.
2. To make pleasing or grateful to the mind or feelings; as, to sweeten life; to sweeten friendship.
3. To make mild or kind; to soften; as, to sweeten the temper.
4. To make less painful or laborious; to relieve; as, to sweeten the cares of life.

   And sweeten every secret tear. - John Keble.

5. To soften to the eye; to make delicate.

   Correggio has made his memory immortal by the strength he has given to his figures, and by sweetening his lights and shadows, and melting them into each other. - John Dryden.

6. To make pure and salubrious by destroying noxious matter; as, to sweeten rooms or apartments that have been infected; to sweeten;;; the air.
7. To make warm and fertile; — opposed to sour; as, to dry and sweeten soils.
8. To restore to purity; to free from taint; as, to sweeten water, butter, or meat.
9. To make more attractive; — said of offers in negotiations, as, to sweeten the deal by increasing the price offered.
10. To become sweet.