The /eɪ/ diphthong is spelled <aCe>, <ai>, <ay> or <ei> in neighs, and occurs in the letter name K. The /ɔɪ/ diphthong is spelled <oi> or <oy>.
This is a contrast between two closing diphthongs with very different starting positions. It is not a problem for learners.
Interesting pairs include:
As the /ɔɪ/ diphthong is fairly rare, the density figure is one of the highest at 13.8%. The set makes 51 semantic contrasts giving a loading of 47.2%.
ail oil ailed oiled ailing oiling ails oils ale oil ales oils allay alloy allayed alloyed allaying alloying allays alloys bail boil bailed boiled bailing boiling bails boils bale boil bales boils baled boiled baling bpoiling bay boy bays boys bay buoy bayed buoyed baying buoying bays buoys bey boy beys boys bey buoy beys buoys braille broil cane coin caned coined canes coins caning coining chase choice chases choices clay cloy daily doily dailies doilies decay decoy decayed decoyed decaying decoying decays decoys distrait destroy fable foible fables foibles faced foist fail foil failed foiled failing foiling fails foils fey Fowey gaiter goitre gaiters goitres grain groin grained groined grains groins haste hoist jade joyed Jane join jay joy jays joys K coy kail coil Kate quoit lain loin lane loin lanes loins later loiter mail moil mailed moiled mailing moiling mails moils male moil males moils mason moisten masons moistens neighs noise paint point painted pointed painting pointing paints points painter pointer painters pointers pays poise play ploy plays ploys ray Roy repaint repoint repainted repointed repainting repointing repaints repoints sail soil sailed soiled sailing soiling sails soils sale soil sales soils say soy survey savoy surveys savoys tail toil tailed toiled tailing toiling tails toils tailor toiler tailors toilers tray troy vale voile
Credit: John Higgins