Why is PhD read as /piːeɪtʃˈdiː/ (from Oxford Dictionary) and not, for example, like /fˈdiː/ , while diagraph ph is read as /f/ in Latin and Greek words? Why do we write Ph if not to represent the /f/ sound?
There are questions about writing (like this) but not pronouncing.
EDIT: Thanks for answers. To be clear. I asked this because of it is not the three letters P.h.D. Why we read it not as /ɛf diː/?