Consonant Doubling in English

Vivian Cook 
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Information on consonant doubling in English, sources at end.

Consonant Doubling (simplified)

Letters that double: <b d f g l m n p r s t z> (<c> in acc-, occ-, succ-)
Letters that do not double: <h j k q v w x y>
Pseudo-doubling: <k> -> <ck>, <ch> -> <tch>, <ge> -> <dge>, <v> -> <ve>, <m> -> <me> (sometimes)

Non-word formation

Simple V+C base-words double consonants to mark the previous simple vowel as short: comma/coma rudder/ruder (alternatively 'Double consonant letters do not normally follow long vowels' Carney 1997, and do not follow non-simple vowels)

Double consonants after stressed short vowels with stress on the last or penultimate syllable; full, stiff, rubber

exceptions: monosyllables: nil, gel, pal, gal; Latinate French words; comet, florid
Monosyllables double to obey 3-letter rule; ebb, inn, egg, add, err

No double consonants in words with primary stress third from end; bigamy, celery, denizen, vilify (third syllable shortening is unmarked in spelling)

Word formation

A. inflections
Simple V+C base-words double consonants before a suffix staring with a vowel; mat matting: funny later/latter mater/matter (but trigger-endings vary)
corollary: no consonant doubling when previous vowel is double: heading

B. prefixes
Double consonants after Latin prefixes beginning <a-, co- e-, i-, o-, su->: addict, address

Exceptions: words with primary stress third from end; bigamy, denizen, vilify, (third syllable shortening is unmarked in spelling)
Unexpected double p in worshipping, kidnapping, handicapping

British versus American styles

British have final <l> in words with more than one syllable: fulfil; American have <ll> fulfill, appall, enroll

Words that do not double in States before <ing ed er/or>; traveling, kidnaped, equaled, counselor; plus woolen, carburetor (British forms are exceptions to normal rule)

 

British 

American

Single versus double l 

appal

appall

 

enrolment 

enrollment

 

skilful 

skillful

 

travelling 

traveling

 

jeweller 

jeweler

 

woollen 

woolen

Words ending in p 

kidnapped 

kidnaped

 

worshipped 

worshiped

Single versus double g 

wagon 

waggon

See American and British style spelling

English consonant doubling according to Carney

Basic (vowel length Carney, 1997)

- A stressed vowel may be marked as short by a following doubled consonant letter in the first two syllables of a minimal free form

- A final <-e> after a single consonant letter in native words will mark the previous vowel as long. This <-e> is usually dropped if a suffix beginning with a vowel is added

- Lexical <-e> marks lapse, tense, etc as single morphemes

- When final in a monosyllabic word, /z/ and // may be marked by a final <-e> even when they occur after two vowel letters, as in please, wreathe

Advanced (Carney, 1994)

D1 Double consonant letters do not normally follow long vowels

D2 Two identical consonant letters may occur in words with a Latinate prefix (ad-, com-, e(x)-, in-, ob-, per-, sub-

D3 The following 15 simple consonants regularly have <C>-doubling in the appropriate contexts: /p b t d k g t d f s z l r m n / <kk> to <ck>, <chch> to <tch>, badge

D4 Stressed short vowels in simple base forms with the primary stress on the last or next to the last syllable are normally marked by <C>-doubling

D5 <C>-doubling does, not, however, usually occur with /p b t d g m n/ before a word boundary

D6 When a primary stress falls on a short vowel which is three or more syllables from the end of a minimal free form, there is no <C>-doubling to mark it

D7 <C>-doubling does not usually occur before the bound-form endings <-ic>, <-id>, <-ish>, <-ule> and Latinate <-it>

D8 <C>-doubling persists in the spelling of a morpheme even when the primary stress is shifted by stress-determining suffixes

D9 Before final / l/ in a word, a previous short vowel is marked by <C>-doubling and the / l/ is pelt with inverted <le> in Basic words

D10 There are several instances in which the general restriction that <C>-doubling does not follow long vowels (#D1) appears to fail in SBS. These involve the 'new' long vowels /a:/, / :l/ and / /

D11. There are letter-sequencing (grapho-tactic) restrictions on <C>-doubling

5 most frequent words with doubled consonants from British National Corpus (out of 100,000,000)
(more or less, as some problems finding them)

Cons  

1

2

3

4

5

B

rubbish
2257

grabbed
1235

rabbit
1048

lobby
974

abbey
966

C

according to 15722

success
13392

account
12695

successful 10803

access
9499

D

suddenly 11795

additional 7364

added
6572

middle
4783

address
4783

F

off
35628

office
25587

effect
22509

staff
22227

difficult
22033

G

suggests
6720

biggest
4632

suggest
4594

suggested 4485

eggs
3713

L

will
244822

all
227737

well
96080

'll
72591

still
71717

M

mm
33893

community 22146

programme 18936

committee 18864

common 16938

N

dinner
6294

annual
7754

inner
4471

planning
6593

runners
790

P

support 17156

approach 13076

happy
11649

appropriate 11010

opportunity 10120

R

current 12141

sorry 11435

tomorrow 9243

marriage 7858

carry
7064

S

possible 34178

business 33573

less
25147

process
22570

across
21763

T

little
24572

getting
20355

better
20343

committee 18864

matter
16375

V

skivvy
37

navvy
25

savvy
15

lavvy
13

civvy
13

Z

jazz
1159

puzzled
644

puzzle
430

pizza
353

dizzy
324

Doubling Mistakes in English by L2 users

A Adding an unnecessary  consonant

B Not doubling a consonant

accross (Spanish)
affraid (Chinese)
affraid (French)
allarm (Arabic)
allmost (Chinese)
allways (German)
appart (apart) (Spanish)
assissting (Chinese)
beautifull (German)
bigginer (Arabic)
borring (French)
bussines (Spanish)
bussiness x2 (Chinese)

bussiness (Italian)
bussiness x2 (Spanish)
bussinessman (Chinese)
bussinessmen (Japanese)

callender (Italian)
carefull (French)
carefull (German)
comming  (French)
comming  (German)
controll (Japanese)

cruissing (French)

developpe (French)

evenning (French)

exclussive (Spanish)
familly (French)
finnal (Italian)
focuss (Spanish)
forgett (Japanese)
fundamenntaly (Japanese)

gratefull (French)
gratefull (German)
gratefull (Italian)
gratefull (Spanish)
guaranttee (German)

Hellen (German)
hopping (hoping) (Spanish)
interesstet (Arabic)
interrested (French)
meetting (Chinese)

mentionned (Spanish)

misstakes (Japanese)
monney (French)
neccesary (Spanish)
neccessarily (Arabic)
neccessary 

(French)
obbligation (German
ocassions (Spanish)
occassionally (Spanish)
off course (Japanese)
oppinnion (Italian)
oppinion (Spanish)
organizzing (Japanese)
personn (French)
personnally (German)
pitty (Spanish)

powerfull (French)
proffessional (Spanish)
rennovation (Spanish)
sattelites (Japanese)
saussages  (French)
schollar-days (Spanish)
shopps (Chinese)
sincerelly (Spanish)
smilling (Arabic)
snorring (Chinese)
somme (French)
toilett (Chinese)
tripp (trip) (Arabic)
trully (French)
unfortunatelly (Arabic)
universitty (Chinese)
untill (German)
untill x2 (Italian)
untill (Japanese)
untill (Spanish)
usefull x2 (French)
ussually (Spanish)
verry x3 (German)
verry (Italian)
verry x3 (Japanese)
visitting (Japanese)
wallett (Arabic)
wellcome (French)
wellcome (Spanish)
wenderfull (Chinese)
wonderfull (Arabic)
writte x2 (write) (Spanish)
writting (Chinese)
writting x2 (French)
writting x2 (German)
writting (Spanish)
writting (Italian)

 

accomaditing (Chinese)
accomodate (Chinese)
accomodation (German)
accomodation (German)
accomodation (Italian)
accomodations (Italian)
acompany (Chinese)
addres (Arabic)
adres (French)
adres (Italian)
adress (Spanish)
adress x3 (Arabic)
adress x2(Italian)
adress x3 (French)
adress x4 (German)
adresse x2 (Italian)
adresses (Italian)

adresses (Spanish)

agressive (Japanese)

apears (German)

apreciated (French)

arived (Arabic)

asist x2 (Spanish)

atention x2 (Spanish)

beginer x2 (Spanish)

begining (German)
begining (French)
begining (Spanish)
biger (Italian)
biger (Spanish)
Britany (French)
busines (Spanish)
businesman (German)
cary (German)
cassete (German)
cigarrets (German)
cofee (French)
colaboration (Spanish)
comercial (German)
comittee (French)
comittee (German)
commited (Arabic)

comunicate (German)
comunicate (Japanese)
conected (Spanish)
diferent (Spanish)
dilema (Japanese)
efective (Japanese)
embarassed (French)
exagerating (Arabic)
excelent (Spanish)
exelent (Spanish)
faithfuly (French)
faithfuly (Spanish)
finaly (Chinese)

forgoten (Spanish)

funy (French)

grany (Japanese)

gratefuly (Spanish)

happines (Spanish)

helo ( Italian)

illnes (Spanish)

imigrants (Chinese)

mposible (Japanese)

imposible (Spanish)

inacessible ( French)
indiferent (Chinese)
instalations (French)
inteligence (Spanish)

Jeny's (Chinese)
jewelries (German)
jewelry (Chinese)
kising (Chinese)
lader (French)
litle (Arabic)
litle (Chinese)
maried (Arabic)
mesage (French)
mis (miss) (Spanish)
necesary (Spanish)
necesities (German)
necesity (Spanish)
normaly (Spanish)
ocurred (Spanish)
omelet (Spanish)
oportunity (French)
overlaping (French)
peper (French)
personaly (Chinese)
personaly (Spanish)
polution (French)
posable (French)
poslble (Spanish)
prefered (French)
prefered (Italian)
profesional (Spanish)
proffesional (Spanish)
programes (Japanese)
quareling (Arabic)
quarreling (German)
questionaire (German)
realy (Japanese)
realy (Spanish)
realy x2 (Arabic)
realy x3 (German)
regreted (Italian)
sory (Italian)
specialy (Japanese)
steped (Arabic)
strugling (German)
suceed (French)
sucessful (German)
swiming x2 (French)

tel (tell) (Chinese)

teling (Italian)

terible (Italian)

til (Spanish)

totaly (Arabic)

walet (Arabic)

walet (Italian)

wil (Arabic)

writeen (Japanese)

writen (Chinese)

writen (Japanese)

 

L2 Consonant doubling mistakes

These amount to 14.4% of all L2 mistakes, 43.3% of mistakes with consonant addition or omission. Adding an unnecessary double consonant is 48.3%, omitting a necessary second consonant 51.7%.

Letter Frequencies in English  Silent Letters  I before E  Common spelling patterns