The /r/ sound is spelled with <r> or <rr>. The /j/ sound is spelled with <y>, <qu> in /kj/ clusters and is heard in the letter name U.
This is a contrast between an alvolar retroflex continuant and a palatal semivowel, both voiced. It only ocurs initially or in initial clusters. In spite of the similarity it is not a problem.
Interesting pairs include:
The mean density value is 0.6%. The lists make 48 semantic distinctions, a loading of 61%.
accrues accuse Crewe cue Crewe Q Crewe queue crew cue crews cues crew Q crews Q's crew queue crewed queued crewing queueing crews queues drew dew droop dupe drooped duped drooping duping droops dupes Frome fume overdrew overdue Pru pew rack yak racks yaks rah yah raise yeas ram yam rams yams rank yank ranked yanked ranking yanking ranks yanks rap yap rapped yapped rapping yapping raps yaps rate Yate raw yaw raw yore raw your ray yea rays yeas re ye rear year rears years reeled yield rend yenned Rennes yen ret yet roar yaw roared yawed roars yaws roar yore roar your rob yob robs yobs Roman yeoman roo U roos U's roo you rood you'd roos use roost used rot yacht rots yachts rotted yachted rotting yachting rue U ruse U's rue you rung young ruse use ruses uses screw skew strew stew strewed stewed strewing stewing strews stews Troon tune wren yen wrens yens
John Higgins, Shaftesbury, December 2010.