to make sweet to the taste; as, to sweeten tea.-to make pleasing or grateful to the mind or feelings; as, to sweeten life; to sweeten friendship.-to make mild or kind; to soften; as, to sweeten the temper.-to make less painful or laborious; to relieve; as, to sweeten the cares of life.-to soften to the eye; to make delicate.-to make pure and salubrious by destroying noxious matter; as, to sweeten rooms or apartments that have been infected; to sweeten the air.-to make warm and fertile; -- opposed to sour; as, to dry and sweeten soils.-to restore to purity; to free from taint; as, to sweeten water, butter, or meat.-to become sweet.