Doctor's Appointment

Thinking about this, it seems that _______'s appointment relates to medical people. Doctor, dentist, vet, psychiatrist, eye doctor, etc. You seem to have an appointment 'with' non-medical people. Lawyer, CPA, consultant, parole officer (?), etc.

The only thing I can think of that brings all medical people together is the word 'probe' so maybe if you need to be probed (and are willing to pay for it), you have a ___________'s appointment, otherwise you have an appointment with ___________.

I use the singular. Its always struck my ear right. I have a doctor appointment. lawyer appointment, dentist appointment. this is a fool errand.
then, again, i couldn't place an apostrophe, or, comma, to save my life. maybe this is my way out?

I was thinking that maybe since doctors use to make house calls, an appointment was the doctor's (possessive). It was his to remember. His to get to on time. Hence the apostrophe "s"?

I just heard a re-broadcast of this episode in Dallas. It might be that we say I have a doctor's appointment because we used to go to the Doctor's house for an appointment. I think Doctor's used to have offices and see patients in some part of their house (front, on the side, in the back) or maybe an office attached or close by the house. In both Italian and French, the phrase "I'm going to the doctor's" refers to the idea of going to the doctor's house: "Je vais chez médecin" (in French) and "Vado dal medico" (in Italian). In French "chez" means house. In Italian the the proposition+article "dal" refers either to where someone lives or works.

Love your show by the way!