Last time on Word Routes, we looked at a spelling error that's common enough to show up frequently in edited text: using acclimation when you mean acclamation. That's a case of battling homophones: the two words sound the same, but they have different meanings. The problem crops up with other sound-alikes, such as imminent vs. immanent, compliment vs. complement, principle vs. principal, and of course affect vs. effect. (We talked about that last pair recently in our interview with Jesse Sheidlower of the Oxford English Dictionary.) These mix-ups are particularly insidious because your spellchecker won't bail you out — unless, perhaps, you are using a contextual spellchecker like the one that has been developed for Microsoft Office.

Even when our misspellings don't form other legitimate words, however, we very often goof because of interference from other items in our vocabulary. This is what researchers at Collins Dictionaries, a British publisher, have discovered in a survey of frequently misspelled words. Collins lexicographers analyzed spelling errors using a massive "corpus" of texts (much like the Oxford English Corpus described here). They found that some of the most common errors are ones where we apply our knowledge of how other words are spelled and end up following a false pattern. The number-one culprit? Supersede, which is misspelled as supercede at a very high frequency. The Times of London explains:

Ask ten-year-olds to spell supersede, and there is a good chance they will get it right (or at least they will correctly put an s in the middle) because they will spell it phonetically. But ask adults, and it is quite likely that they will come up with supercede, basing this on their knowledge of the words intercede, precede or cede (from the Latin cedere — to yield).

In truth supersede comes from the Latin supersedere, meaning to desist from. The same temptation to apply knowledge gets us into trouble with another of the most commonly misspelt words, consensus, which is frequently spelt incorrectly as concensus by those who wrongly believe that it relates to the word census. (Census is from the Latin censere — to assess; whereas consensus is from the Latin consentire — to agree).

Although a misinterpretation of Latin often lies at the heart of the problem, more often people make wrong assumptions based on their knowledge of the correct spelling of other, similar words. Many are tempted to spell liquefy as liquify, simply because they know the correct spelling of liquid. Similarly, sacrilegious is often incorrectly spelt as sacreligious because people associate it with religious. The same goes for inoculate, which is often misspelt by those who know that innocuous has a double "n".

As Ian Brookes, managing editor for Collins Dictionaries told the Times, "The real spelling problems occur when people have learnt the rules or have a bit of knowledge, but then make mistakes in how they apply this." British newspapers greeted this news with lighthearted relief. The Times headline reads, "It's proof of what you've always known: you're too clever to be good at spelling." The Mail on Sunday agreed: "Can't spell? Maybe it's because you're too clever, says Collins dictionary."

Of course, it's not really a matter of being too clever, or even being not clever enough. It has more to do with how everyone on the whole spectrum of cleverness acquires the rules of written language and learns to match them up with the rules of spoken language. Linguists talk about this as the correspondence between graphemes and phonemes, and it represents the basic skill of literacy in any language with standard written conventions. In a language like English, however, with so many irregularities between written and spoken forms, we very often take a rule that applies to one word (or a family of words) and try to extend it where it doesn't belong, through the process of analogy. The pattern-matching faculty of our brains comes into conflict with a system where patterns don't always hold very well.

Proponents of "simplified spelling" in English argue that we would be spared these confusions if we chose an orthographic system that better reflects the patterning of speech. But as the linguist Dennis Baron recently wrote, complaints about the irregularity of English spelling have been around since the Middle Ages, and all efforts at widespread reform have invariably failed. Noah Webster, whose 150th birthday we're celebrating this year, had some modest successes in spelling reform, but all he really accomplished was to create a more marked difference between American spelling and that of the United Kingdom and other Commonwealth countries: honor vs. honour, center vs. centre, and so forth. The sad truth is that we're stuck with the spelling conventions we've inherited, even if they're sometimes baffling. But at the very least we can try to get a better handle on the sources of our bafflement.

Click here to read more articles from Word Routes.

Ben Zimmer is language columnist for The Wall Street Journal and former language columnist for The Boston Globe and The New York Times Magazine. He has worked as editor for American dictionaries at Oxford University Press and as a consultant to the Oxford English Dictionary. In addition to his regular "Word Routes" column here, he contributes to the group weblog Language Log. He is also the chair of the New Words Committee of the American Dialect Society. Click here to read more articles by Ben Zimmer.

The case of the tricky schwa.
The OED has been revamping entries, including the ones for "affect" and "effect."
Behold the Corpus
Lexicographers learn the real facts of usage by analyzing enormous collections of texts.