r is used for an approximant in English by a number of well respected phoneticians including Daniel Gimson John C Wells and Peter Ladefoged As long as the discussions defines what is meant by r that s perfectly acceptable and as long as only English is under discussion it s not ambiguous But if both English and Spanish are under discussion of course you don t want to use r for both English red and Spanish rojo because that would be very confusing It s the same with Irish and Hungarian as long as only Irish or only Hungarian is under discussion there s nothing wrong with using for their respective palatal stops however different they may be But if you re discussing both Irish and Hungarian of course you ll want to be more specific about their relative places of articulation gr