When someone declines something, it often carries an implication of regret or unwillingness, suggesting a softer or more diplomatic approach. Refusing, however, may imply a determined or deliberate decision, often without indicating regret or hesitation.

Decline means to turn something down. If someone offers you a drink and you say no, you have declined. Refuse means a hard no, if someone asked you to do something you don’t want to, you can refuse which means you won’t do it under any circumstance.