To make sweet to the taste.
to sweeten tea
To make (more) pleasant or to the mind or feelings.
to sweeten friendship
To make mild or kind; to soften.
to sweeten the temper
To make less painful or laborious; to relieve.
to sweeten the cares of life
To soften to the eye; to make delicate.
To make pure and salubrious by destroying noxious matter.
to sweeten rooms or apartments that have been infected
To make warm and fertile.
to dry and sweeten soils
To restore to purity; to free from taint.
to sweeten water, butter, or meat
To make more attractive; said of offers in negotiations.
To become sweet.