A rhotic accent (for instance, in Los Angeles or Edinburg) is one where r can be heard in all the places where it is found in the spelling (and a few extra - look up the American pronunciation of the word 'colonel' for instance! )
So in a rhotic accent, the r is heard in both 'car' and 'park'.
car park farmer
While a non-rhotic accent (for instance, in London or Sydney Australia) only has the r-sound if the next sound is a vowel - so not at the end of a word, as in 'car', or before a consonant, as in 'park'.
See below for further discussion.
car park farmer
Areas encircled by blue are rhotic: 'farmer' =
Areas encircled by red are non-rhotic: 'farmer' =
In the lightly-shaded red area on the East Coast of the USA the number of non-rhotic speakers is getting smaller; on the other hand the non-rhotic area in the British Isles is getting larger.
Note too that this map does not show small details: in the Caribbean, for instance, most varieties of English are non-rhotic, but Barbados stands out as fully rhotic (Wells 1982 582-5). Urban Scottish accents may occasionally be non-rhotic, and residual areas of rhotacism may linger in the rhotic area of England shown below. Wells also mentions reports of rhoticism from South Island, New Zealand (606).
This map also fails to show areas in Africa, India and the Far East where English may be spoken as a first language.
Maps modified from http://mapweb.parc.xerox.com/map - thanks!
If you think for a moment, you'll realise that spelling cannot really have anything to do with it. Langages have been spoken on this planet for thousands of years, perhaps hundreds of thousands, and spelling is only a very recent invention. Children and illiterates are rhotic and non-rhotic just the same as anyone else, although they have no idea whether there should be an 'r' in a word or not. And it's not very likely that people who can read or write use this knowledge to work out whether to pronounce an 'r'.
So how would we describe the difference in pronunciation between illiterate Americans and illiterate Brits? In fact it's very simple. We can simply say that in a non-rhotic accent, r only occurs if a vowel follows. In rhotic accents, r does not need a following vowel.
So, if we write "V" for any vowel:
This description of the difference between rhotic and non-rhotic accents of English works for all speakers, regardless of their spelling abilities, and explains a lot when it comes to understanding linking r .
a rhotic accent can have the sequences rV, VrV, and Vr; but a non-rhotic accent can only have rV and VrV.
If you have any questions mail me at firstname.lastname@example.org.