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The plural of "quiz" is spelled with double "z" while the plural of "box" (and sometimes "bus") is spelled with single last consonant. Why is it so? Is this the general rule to double the last consonant to keep the syllable closed?

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Busses is a valid plural of bus. Merriam-Webster, Wiktionary, The Free Dictionary. – RegDwigнt May 9 '12 at 8:23
@RegDwightΒВBẞ8, all of the dictionaries you have mentioned also list "buses" as a valid plural of "bus". Citing Merriam-Webster "plural bus·es also bus·ses", this makes me think that "buses" is more common. – Larisa Lyapina May 9 '12 at 9:24
@LarisaLyapina - Buss is an old word for "kiss"; it may be that the single-S variant gained popularity out of a desire to avoid confusion. Maybe. – MT_Head May 9 '12 at 9:40
@LarisaLyapina,MT_Head: Per this earlier question, the vehicles are normally pluralised as buses, and the electronics data/power connections as busses. – FumbleFingers May 9 '12 at 14:42
up vote 3 down vote accepted

In most cases where a word ends in (vowel)-(consonant)-e, we pronounce the last syllable with a long vowel sound. Conversely, most words that end with a double consonant get a short vowel sound.

So: when adding "es", "er", "est", or "ed" to the end of the word would appear to change the vowel sound, double the consonant.


  • quizes - ize is usually pronounced like "eyes", so change it to quizzes to preserve the short I sound

  • subed (short for "substituted") - ube is usually pronounced "oob" or "yoob", so change it to subbed

  • biger - ige is usually pronounced "eyej", so change to bigger

Related: Tom Lehrer's song Silent E from The Electric Company TV show (one of my childhood faves!)

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I find this answer a bit unsatisfactory. The rules for doubling the consonants before -ed, -ing, and -er/-est are pretty much clear and follow the logic of your answer. However, the plural -es seems to be different. Why is it buses, but not busses? If bus were an adjective or verb, we'd have bussed, bussing, or busser, and the bussest... But somehow it's buses. – Armen Ծիրունյան May 9 '12 at 11:03
Wouldn't you think that if "quizes" should rhyme with "eyes", then "buses" should rhyme with "fuses"? – Malvolio May 9 '12 at 14:54
@Malvolio - Which of us were you addressing? – MT_Head May 9 '12 at 16:04
@ArmenTsirunyan - Bus is a relatively new word, dating from 1825 or so - it's short for omnibus - which means that all of those forms you mention are even newer. As I said in a comment to the OP, buss (meaning "kiss") was already a word in (declining) use at the time. I suspect that buses, busing, bused, etc. were all coined that way to avoid collision with the existing words. Over time, as "buss" dropped even further from common use (I've only ever seen it used in Heinlein novels), I suspect that the reason for the distinction has been largely forgotten. – MT_Head May 9 '12 at 16:11
When I was growing up (1942-60, say), busses was the accepted plural spelling for bus. Later, when the derived noun bussing was introduced in a context of undoing school segregation, it quickly got shortened to single-S busing by headline writers, and soon enough by everybody else. A letter saved is a letter earned, or something. The fact that jokes about "busing" and "abusing" were easier to make with this spelling is undoubtedly accidental. – John Lawler May 9 '12 at 16:21

When there are two vowels before a consonant, you do not double the consonant; however, qu has its own sound, so the u is not "counted" as a vowel.

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