sweeten

Short definition from Wiktionary

Verb

1. 1
   To make sweet to the taste.
2. 2
   To make (more) pleasant or to the mind or feelings.
3. 3
   To make mild or kind; to soften.
4. 4
   To make less painful or laborious; to relieve.
5. 5
   To soften to the eye; to make delicate.
6. 6
   To make pure and healthful by destroying noxious matter.
7. 7
   To make warm and fertile.
8. 8
   To raise the pH of (a soil) by adding alkali.
9. 9
   To restore to purity; to free from taint.
10. 10
    To make more attractive; said of offers in negotiations.
11. 11
    To become sweet.
12. 12
    To supplement (a composition) with additional instruments, especially strings.

Proper noun

1. 1
   A surname.