English Nasals and Spelling

English spelling is famously not phonetic. By which people usually mean that words are not always “spelled the way they are pronounced.”  Would be spelling reformers might be warned, however, that a perfectly phonetic system might pose its own problems.  Recently, I encountered an irregularity in English spelling that arises from being too faithful to pronunciation:

The rule is the following: The prefixes CON- and IN- are spelled with an M if they attach to a word starting with B, P or M.  Otherwise, use N. There are exceptions, of course, the most common being “comfort” and a few loanwords like “comrade.”  The why of this rule will require a short side-trek through the sound system of English.

English has three nasal phonemes (language-sounds that are produced by letting the breath out through the nose): N, M and NG.  Language-sounds are defined by their ability to distinguish between otherwise identical words, so therefore we can put a hotdog in a BUN, call our lazy roommate a BUM and plug a hole in a wine cask with a BUNG.  

The trouble with nasals is that they relent to peer pressure really easily.  So, whenever an nasal sound sits in front of another consonant, it is generally going to be pronounced with the exact same mouth shape as the following sound.  Thus “think” is really pronounced /thi-ng-k/, with the NG of “thing” not the N of “thin.”

Likewise, a simple word can end with “mp”, but not “mt” or “mk.”  Try pronouncing the following:

1. imp
2. imt
3. imk

Because the M and P are pronounced with the same mouth shape, the first is a real word, the second is more difficult to produce and the third is nearly impossible to say fluidly, at least on a first try.

Which brings us to the prefixes “IN-” (meaning not-) and “CON-” (meaning with-).  The impressionable nature of their N's extends across syllables.  Since we never write “ng” anywhere but the end of the word, this leaves “incorrect” and “congress” unchanged, even though they are pronounced /ing-korect/ and /kong-gres/ most of the time.

However, when these prefixes are attached to a word beginning with a front of the mouth sound like P, B or M, they are spelled exactly as they are pronounced: “impossible,” “combustion” and “commiserate.” 

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PS for linguistic nerds:


[1] This rule was developed to help a client at the reading intervention center where I work.  It is interesting to me because her difficulty with “com-” and “con-” endings was not due to the usual hobgoblins of English spelling but with her difficulty distinguishing between the phonemes N, M and NG.  To her, both prefixes all sounded alike, and thus arose the need for a simple spelling rule until a greater level of phonemic awareness could be developed.


[2] Just off the top of my head, it seems that progressive nasal assimilation only applies to derivational suffixes, since the inflectional suffix [-ed] does not effect a word final nasal's place of articulation:  neither “rimmed” and “ringed” are  pronounced /rind/.  This is what we would expect if the nasal assimilation rule is applied after derivation but before inflection.