1 [I] to become weaker, smaller or less good 变弱；变小；衰退: declining profits 不断减少的利润The standard of education has declined in this country. 这个国家的教育水平下降了。

2 [I,T] (formal 正式) to refuse, usually politely 婉拒；（礼貌地）拒绝: Thank you for the invitation but I'm afraid I have to decline. 谢谢你的邀请，但很抱歉，我不得不推辞。

3 [I,T] (grammar语法) if a noun, an adjective or a pronoun declines, it has different forms according to whether it is the subject or the object of a verb, whether it is in the SINGULAR or plural, etc. When you decline a noun, etc, you list these forms. 使（名词、形容词或代词）发生词尾变化