dear jack，

　　we will have a graduation ceremony next week.and i strongly suggest you attend.because this is a great honor to us .

　　example 2 formal reply ( decline )谢绝mr. and mrs. george mailer present their compliments to mr. and mrs. robert, and regret that a previous engagement prevents them from accepting the kind invitation to dinner on friday, march 26th. 17 butter place march 22nd

　　常用的英文邀请信

　　dear sir/madam:

　　im delighted you have accepted our invitation to speak at the conference

　　in [city] on [date].

　　as we agreed, youll be speaking on the topic "" from [time] to [time]. there

　　will be an additional minutes for questions.