lessen

lessen
/ˈlesn; `lɛsn/ v
1 [I] become less 变少: The pain was already lessening. 疼痛正在减轻.
2 [Tn] reduce (sth) 减少（某事物）
    lessen the impact, likelihood, risk of sth 减少某事物的影响、 可能性、 冒险性.

牛津英汉双解词典