User:JackLumber~enwiktionary/Doubled consonants

Doubled in British English
The final consonant of an English word is sometimes doubled when adding a suffix beginning with a vowel. Generally this occurs only when the word's final syllable ends with a single vowel followed by a single consonant, and the syllable is stressed; but in British English, a final -l is often doubled even when the final syllable is unstressed. This exception is no longer usual in American English, apparently due to Noah Webster. The -ll- spellings are nonetheless still regarded as acceptable variants by both Merriam-Webster Collegiate and American Heritage dictionaries, and are regularly used by some publications (notably The New Yorker).
 * The British English doubling is required for all inflections and for the suffixes -er, -or. Therefore, British modelling, quarrelled, cruellest, traveller, counsellor; American usually modeling, quarreled, cruelest, traveler, counselor.
 * parallel keeps a single -l- in British English, as in American English (paralleling, unparalleled), to avoid a cluster -llell-.
 * Words with two vowels before l are covered where the first either acts as a consonant (UK equalling, initialled; US usually equaling, initialed) or belongs to a separate syllable (UK fu•el•ling, di•alled; US usually fu•el•ing, di•aled)
 * But British woollen is a further exception (US woolen); also, wooly is accepted in America though woolly dominates in both.
 * Endings -ize/-ise, -ism, -ist, -ish usually do not double the l in British English: normalise, dualism, novelist, devilish
 * Exceptions: tranquillise; duellist, medallist, panellist, sometimes triallist
 * For -ous, British English has a single l in scandalous and perilous, but two in marvellous and libellous.  For -ee, British English has libellee.
 * American English has unstressed -ll-, as in the UK, in some words where the root has -l. These are cases where the alteration occurs in the source language, often Latin. (Examples: bimetallism, cancellation, chancellor, crystallize, excellent, tonsillitis)
 * But both dialects have compelled, excelling, propelled, rebelling (notice the stress difference); revealing, fooling (double vowel before the l); hurling (consonant before the l).
 * Canadian and Australian English largely follow British usage.

Among consonants other than l, practice varies for some words, such as where the final syllable has secondary stress or an unreduced vowel. In the U.S., the spellings kidnaped and worshiped, introduced by the Chicago Tribune in the 1920s, are common alongside kidnapped and worshipped, the only standard British spellings.

Miscellaneous:
 * British calliper or caliper; American caliper.
 * British jewellery; American jewelry. According to Fowler, jewelry used to be the "rhetorical and poetic" spelling in the UK. Canada has both. Likewise, Commonwealth (including Canada) has jeweller and U.S. has jeweler for a jewel(le)ry retailer.

Doubled in American English
Conversely, there are words where British writers prefer a single l and Americans usually use a double l. These include wil(l)ful, skil(l)ful, thral(l)dom, appal(l), fulfil(l), fulfil(l)ment, enrol(l)ment, instal(l)ment. In the UK ll is used occasionally in distil(l), instil(l), enrol(l) and enthral(l)ment, and often in enthral(l). Former spellings instal, fulness, and dulness are now rare. The Scottish tolbooth is cognate with toll booth but has a specific distinct sense.

The preceding words have monosyllabic cognates always written with -ll: will, skill, thrall, pall, fill, roll, stall, still. Comparable cases where a single l occurs in American English include full→useful, handful, etc.; all→almighty, altogether, etc.; null→annul, annulment; till→until; well→welfare, welcome; toll→extol; spell→dispel; chill→chilblain; and others where the connection is less transparent. Note that British fulfil and American fulfill are never fullfill or fullfil.

Dr Johnson wavered on this issue; his dictionary of 1755 lemmatises distil and instill, downhil and uphill.