Earlier today I spelled "infered" with one R and my handy editor promptly added some red squiggles.

Acknowledging the error of my ways I added the missing R happy carried only writing my document.

Moments later I had to write the word "inferrence" and, remembering the lesson taught to me by my electronic dictionary, I diligently used two Rs.

Sadly, the red squiggles appeared once again, telling me I hadn't quite learned my lesson yet.

So, why is it that "Inferred" is spelled with two Rs when it's cousin "Inference" only has one?

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    If it were pronounced inFERRence, it would be spelled with two r's. Commented Oct 19, 2018 at 14:21
  • @PeterShor - which came first, the spelling or the pronunciation? Also, the way things are pronounced from one vernacular to another vary considerably. Commented Oct 19, 2018 at 14:23
  • The pronunciation came first. The rule (although if you look around for exceptions, you'll find lots of them) is that you only double the consonant after an accented syllable. Consider inferred and offered. Commented Oct 19, 2018 at 14:32
  • 1
  • becuase of the way the preterite is formed with some simple verbs. the -ed some times takes a dental before it (like (-ted) or (-ded)).
    – Carly
    Commented Jun 4, 2019 at 17:52

2 Answers 2


Monosyllabic words are not a problem: you know when to double a final consonant before adding a suffix, since the vowel in the word is always stressed:

rob+ed/ing/er = one final consonant preceded by one stressed vowel > double consonant: robbed, robbing, robbery, a robber

Words made of more than one syllable can be a bit of a problem:

The stressed syllable in the verb "to infer" is the second one.

So the rule which goes "before adding a suffix to a word, double its last consonant if the word ends in ONE CONSONANT only, preceded by ONE STRESSED VOWEL only" applies to the verb forms (past simple, past participle, -ing form).

infer+ed/ing = one final consonant preceded by one stressed vowel > double consonant: he inferred that… / he has inferred that… / inferring that…

But in the noun "an inference", the stress is moved to the first syllable. A case a bit similar to the noun "an increase" opposed to the verb "to increase". So, before you add the noun suffix –ence, you have a word "infer" ending in one consonant all right, but preceded by one UNSTRESSED vowel this time.

infer+ence = one final consonant preceded by one unstressed vowel > single consonant: an inference

Whereas in words like "to differ" and "a difference", the stressed syllable remains the same, the first one, and, as a result, the last consonant is doubled neither in the verb forms, nor in the noun:

differ+ed/ing/ence = one final consonant preceded by one unstressed vowel > single consonant: one thing differed from another / one thing has differed from another / differing from something / a difference

However, there are exceptions to this rule!

Michael Swan, in Practical English Usage, 2nd edition, 1995, Oxford University Press, wrote, on page 558:

"In British English, we double -l at the end of a word after one vowel letter in most cases, even in unstressed syllables.

travel > travelling; equal > equalled

In American English, words like this are normally spelt with one l: traveling.

other exceptions:

Consonants are sometimes doubled at the end of final syllables that are pronounced with full vowels (e.g. /æ/), even when these do not carry the main stress.

kidnap > kidnapped; handicap > handicapped; worship > worshippers (US also worshipers); combat > combatting or combating

Final -s is sometimes doubled in focus(s)ing, focus(s)ed, bias(s)ed, and similar words.

  • I think this is sort of half right. The stress-related rule about consonant doubling is why inferred has two Rs. But in fact, the rule about consonant doubling doesn't apply to all kinds of suffixes, and I think it's a bit dubious to say that it apples to -ence: we have the word excellence which is stressed on the first syllable.
    – herisson
    Commented Jun 2, 2019 at 10:42
  • @sumelic: Right you are! But there is another "rule", an exception to the above, saying that, in British English mostly, words ending in one vowel (stressed or unstressed) + l also double the consonant before adding a suffix: cancel > cancelled, cancelling (BrE) canceled, canceling (AmE); travel > travelled, travelling, traveller (BrE) traveled, traveling, traveler (AmE), etc. 'Cancellation' has two ls in AmE... I cannot understand why! Adding the suffix -tion to a word moves the stress from wherever it was to the penultimate syllable, but that does not explain anything here!
    – user58319
    Commented Jun 4, 2019 at 18:37
  • As I said in my last comment, I don't think the usual rule for doubling should be viewed as applying to all kinds of suffixes. It's only certain suffixes, mainly inflectional ones and some productive derivational ones, that follow the "doubling rules" (e.g. the suffixes -ing, -ed, -y, -er, -able). For many words with other endings, the use of double consonant spellings isn't based on the pronunciation, but on etymology.
    – herisson
    Commented Jun 4, 2019 at 20:48

It's yet another oddity of English taking Latin words. The Latin word inferre means "to bring in" (more or less). It's then easy to see how "inferred" came to be. But in 15th/16th century English, Latin endings (not even always suffixes, just endings) began being stripped from words. We gained "infer" to mean what inferre means. But, English being English, different spellings were VERY common. Standardization of the language didn't really even start until hundreds of years later. Prescriptivists and descriptivists fought a not-so-bloody battle, and now we have words that build differently than we expect because they were put into common usage.

As a brief aside, if you (or other readers here) are interested in these sorts of things, there's a book called Word by Word by Kory Stamper, a lexicographer for Merriam-Webster. She discusses quite a bit why words are the way they are. Also, dictionaries are not the key of perfection in English - they are actually written based on common usage. If we all started writing infered, given a decade and an edition or two, the spelling in the dictionary would likely change to follow suit.

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    This is not correct, I’m afraid. The fact that the Latin infinitive happens to have two r’s is incidental – the stem itself has only one r, and that is what’s relevant for the English verb. Infer itself happens to be fairly late, from the 16th c., but others like transfer and refer are from the 1300s, taken from French where they only have one r (transferer, referer). The French infinitive marker -er was dropped when borrowing verbs, and -fer was the result. The subsequent doubling of the r then follows the broad stress-based rule given in user58319’s answer. Commented Jun 2, 2019 at 10:54

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