The /m/ sound is spelled with <m>, <mm> or <mb> in limb. The /ŋ/ sound is spelled with <ng>.
This is a contrast between two voiced nasal continuants, only occurring in medial or final position and widely spaced in the mouth. It is not a problem.
Interesting pairs include:
The mean density value is low at 0.4%. The lists make 29 semantic distinctions, a loading of 48%.
brim bring brimming bringing brims brings bum bung bummed bunged bumming bunging bums bungs clam clang clammed clanged clamming clanging clams clangs clamour clanger clamorous clangorous clamours clangers dumb dung gamma ganger gammas gangers ham hang hammed hanged hamming hanging hams hangs hammer hangar hammers hangars hum hung limb ling limbs lings Pam pang paynim paining prom prong proms prongs ram rang rhomb wrong rhombs wrongs rim ring rimmed ringed rimming ringing rims rings rum rung Sam sang simmer singer simmers singers slam slang slammed slanged slamming slanging slams slangs slim sling slimmer slinger slimming slinging slims slings slum slung some sung strum strung sum sung swim swing swimming swinging swims swings swum swung tammy tangy trim Tring whim wing whims wings
John Higgins, Shaftesbury, December 2010.