Double consonants

Double consonants appear when adding a suffix if the base word uses the so-called "short" sound of a vowel. See So-called “short” and “long” vowels.

For example, “hop” gives “hopped”, with a double consonant in addition to the suffix -ed. Similarly “fat” gives “fatter”, with a t in addition to the suffix -er.

Magic e explains the necessity of consonant doubling. Take the verb “hope”. If we just add “-ed” then we have “hoped” (note that we compressed two “e”s in order not to have “hopeed”). But suppose we want to add an “-ed” to “hop” and at the same time preserve its vowel sound? Obviously if we write “hoped” we will have the same word as before. In order to indicate the correct vowel sound in “hop” we double the previous consonant to produce “hopped”.

Normally "kk" is not used (exception: trekking); what is used is "ck".

Double consonants are used also in the middle of words with no suffixes. For example in “follow” (/ɒ/ sound) and “solar” (/əʊ/ sound). However “solid” also has an /ɒ/ sound, and no double consonant. Based on this example we generalize as follows: the double consonant pattern shows that the vowel has its short sound (or schwa) but a single consonant cannot be used to determine the pronunciation.

Double consonants at the end of a word
Double consonants at the end of a word are normally redundant as these examples show:


 * A as /æ/: add - bad
 * E as /e/: egg - leg
 * I as /ɪ/: inn - win
 * O as /ɒ/: odd - god
 * U as /ʌ/: mutt - cut
 * Y as /ɪ/: chlorophyll - pterodactyl

The table below shows single or double consonants at the end of the word preceded by a single vowel. Uncommon patterns are indicated with yellow.

A + double consonant is /æ/ or /ə/
The real rule is: A + double consonant is (almost) never /eɪ/

See also
 * IPA phoneme /æ/
 * Decoding the letter A
 * So-called “short a”


 * As /æ/: channel - happy - package - traffic
 * As /ə/: account - address - again - around

Exceptions
 * As /eɪ/: bass (in music)
 * As /ɔː/: all - ball - call - caller - fall - hall - small - smaller - tall - taller

Exceptions only in British English
 * As /ɑː, æ/: class - classes - giraffe - glass - pass - passing - staff - staffed

E + double consonant is /e/ or /ə/
The real rule is: E + double consonant is never /iː/

See also
 * IPA phoneme /e/
 * Decoding the letter E
 * So-called “short e”


 * As /e/: better - effort - letter - pepper - success - well

Exceptions:
 * As /ɪ/: effect - efficient - essential - pretty

I + double consonant is /ɪ/ or /ə/
This rule also means I + double consonant is never /aɪ/

See also:
 * IPA phoneme /ɪ/
 * Decoding the letter I
 * So-called “short i”


 * As /ɪ/: innocent - little - middle - miss - still - village

O + double consonant is /ɒ/ or /ə/
This rule means O + double consonant is seldom /əʊ/

See also:
 * IPA phoneme /ɒ/
 * Decoding the letter O
 * So-called “short o”


 * As /ɒ/: comment - occupy - office - opportunity
 * As /ə/: colloquial - communication - occur - official

Exceptions:
 * as /əʊ/: controlled - patrolled - poll - roll - scroll - stroll - stroller - toll
 * As /ʌ/: sonny - tonne

U + double consonant is /ʌ/ or /ə/
This rule means U + double consonant is never /juː/ or /uː/

See also:
 * IPA phoneme /ʌ/
 * Decoding the letter U
 * So-called “short u”


 * butter - dummy - funny - runny - summer - sunny

Exceptions:
 * As /ʊ/: bull - bullet - full - pull

Y + double consonant is /ɪ/ or /ə/
This rule also means Y + double consonant is never /aɪ/

See also:
 * Decoding the letter Y


 * As /ɪ/: syllable - syllogism - symmetrical - yttrium
 * As /ə/: odyssey

R and double consonants
In the sequence VrrV, where V is a vowel sound, the spelling "rr" is used for two different sounds. The “short” sound of the vowel (as in carry) and the rhotic monophthong (as in starry.) This second sound is used only when adding suffixes. For example if we add -ed to occur we double the consonant and we get occurred.

Minimal pairs
(*) Not a minimal pair, because the consonant also sounds differently


 * Other cases

"ss" vs. "s"
In most of the following pairs "ss" is a digraph that sounds /s/. In most examples "s" sounds /z/.

Homophones

 * ad, add; desert (v.), dessert; in, inn;