I thought I spoke English

4 days in Oxford and I realize I don't really speak English after all. So far I've learned that a dual carriageway is a divided highway; an articulated lorry is a tractor trailer; and a detour is a diversion. 

This week a letting agent asked me if my husband was a medical doctor.  I replied no.  She then ask if he was a D Phil.  Again I said no.  "Then what kind of doctor is he?"   I didn't know that in England a D Phil is a doctor of philosophy, or, in U.S. English, a PhD.  

I thought I spoke English.