The Definition of Appointment
  Appointment is a kind of expression which is used to conduct an appointment.

Expressions We Can Use to Make and Accept an Appointment  
  Here are some expressions we can use to make and accept an appointment.

[•]Making an Appointment
 1.Will you go out with me ….? (example: tonight)
 2.I’d like to make an appointment with …. (examples: you, him, her)
 3.Will you pick me up at ….? (example: tomorrow morning 2 p.m.)
 4.Can I come and see you?
 5.Can we meet at …. (examples: Kitchen Restaurant, Hotel) 

[•]Accepting an Appointment
1.Okay. I’ll be there on time.
2.No problem. I’m free …. (examples: on Sunday, at that day, at that time)
3.Sure, I love it.
4.Good idea.
6.All right, see you there.
 •Expressions We Can Use to Cancel an Appointment
1.I’m sorry. I can’t meet you today. I have to see my dentist. Can we reschedule?
2.We’re terribly sorry we have to cancel our appointment. Mr. Tanaka’s flight is delayed for two hours.
3.I’m afraid I have to put off put appointment because I have an urgent business to do.
4.Sorry. I can’t meet you this weekend since I have another appointment.
5.Sorry, I can’t meet you tomorrow. I’m busy at that day.

[-]Dialog 1 (Accepting an Appointment)
Daniela           : Let’s see Aunt Michelle in the hospital.
Cliff                : I’m sorry, not now.I have to finish the homework and send it to Ms. Rita.
Daniela           : What about tomorrow afternoon at 4 p.m.?
Cliff                : Tomorrow afternoon at 4 p.m.? O.K.
The sentences in bold are used to make and accept an appointment. In the dialog, Daniela makes an appointment with Cliff to see Aunt Michelle in the hospital tomorrow afternoon at 4 p.m. Then, Cliff accepts the invitation by saying, “Tomorrow afternoon at 4 p.m.? O.K.”.
[-]Dialog 2 (Cancel an Appointment)
Rose    : Hello Eva. I’m glad to meet you here. I want to say something with you.
Eva      : Are you? Is there something wrong?
Rose    : Yes. I have to postpone our appointment to visit Lelly this afternoon.
You know, I have to finish my assignment and collect it tomorrow. I’m sorry.
Eva      : That’s O.K. Maybe some other time.
The sentence in bold is used to cancel an appointment. In the dialog, Rose has to cancel the appointment because she has an assignment to finish. Although Rose cancels the appointment, Eva is alright. She says that she’s O.K. with that.