American and British English pronunciation differences

Differences in pronunciation between American English (AmE) and British English (BrE) can be divided into
In the following discussion:
Stress.
Subscript a or b means that the relevant unstressed vowel is also reduced to or in AmE or BrE, respectively.
French stress.
For many loanwords from French, AmE has final-syllable stress, while BrE stresses an earlier syllable. French loanwords that differ in stress only are listed below.
Verbs ending in "-ate".
Most 2-syllable verbs ending in "-ate" have first-syllable stress in AmE and second-syllable stress in BrE. This includes "castrate", "collate", "cremate"A2, "curate", "dictate"A2, "donate"A2, "frustrate", "gradate", "gyrate", "hydrate", "locate"A2, "migrate", "mutate", "narrate"bA2, "phonate", "placate"bB2, "prostrate", "pulsate", "rotate", "serrate"A2, "spectate", "stagnate", "striate", "translate"A2, "truncate", "vacate"b*A2, "vibrate"A2. Examples where AmE and BrE match include "conflate", "create", "debate", "equate", "elate", "inflate", "negate"; and "mandate" and "probate" with first-syllable stress. Derived nouns in "-ator" retain the distinction, but those in "-ation" do not. Also, "migratory"B2 and "vibratory"B2 sometimes retain the distinction.
Most longer "-ate" verbs are pronounced the same in AmE and BrE, but a few have first-syllable stress in BrE and second-syllable stress in AmE: "elongate"aA2, "impregnate", "inculcate", "inculpate", "infiltrate"A2, "remonstrate"abA2, "sequestrate", "tergiversate"aA1. For some derived adjectives ending "-atory" stress-shifting to "-a(tory)-" occurs in BrE. Among these cases are "celebratory"a (BrE: ), "compensatory"a, "participatory"a, "regulatory"aB1. AmE stresses the same syllable as the corresponding "-ate" verb (except "compensatory", where AmE stresses the second syllable). A further "-atory" difference is "laboratory"B2: AmE and BrE .
Miscellaneous stress.
There are a number of cases where same-spelled noun, verb and/or adjective have uniform stress in one dialect but distinct stress in the other (e.g. "alternate", "prospect"): see initial-stress-derived noun.
The following table lists words not brought up in the discussion so far where the main difference between AmE and BrE is in stress. Usually, it also follows a reduction of the unstressed vowel. Words marked with subscript A or B are exceptions to this, and thus retains a full vowel in the (relatively) unstressed syllable of AmE or BrE. A subsequent asterisk, *, means that the full vowel is "usually" retained; a preceding * means that the full vowel is "sometimes" retained.
Words with other points of difference are listed in a later table.
Affixes.
"-ary, -ery, -ory, -mony, -ative, -bury, -berry".
Where the syllable preceding the suffixes "-ary", "-ery", "-ory", "-mony" or "-ative" is unstressed, AmE pronounces the penultimate syllable with a full vowel sound: for "-ary" and "-ery", for "-ory", for "-mony" and -ative. BrE reduces the vowel to a schwa or even elides it completely: or (hereafter transcribed as in diaphonemic transcription), and . So "military" is AmE and BrE , "inventory" is AmE and BrE , "testimony" is AmE and BrE and innovative is AmE or and BrE . (The elision is avoided in carefully enunciated speech, especially with endings "-rary","-rery","-rory".)
Where the syllable preceding "-ary", "-ery", "-ory", "-mony" or "-ative" is stressed however, AmE also usually reduces the vowel: , . Exceptions include "library", "primary"A2, "rosemary". (Pronouncing "library" as rather than is stigmatized in the United States, for example as associated with African-American Vernacular English, whereas in BrE, is common in rapid or casual speech.)
The suffix "-berry" is pronounced by similar rules, except that in BrE it may be full after an unstressed syllable, while in AmE it is usually full in all cases. Thus we have "strawberry": BrE , AmE , and "whortleberry": BrE/AmE .
The placename component "-bury" (e.g. "Canterbury") has a similar difference: AmE has a full vowel: where BrE has a reduced one: .
Note that stress differences between the dialects occur with some words ending in "-atory" (listed above) and a few others like "capillary" (included in #Miscellaneous stress above).
Formerly the BrE–AmE distinction for adjectives carried over to corresponding adverbs ending "-arily", "-erily" or "-orily". However, nowadays some BrE speakers adopt the AmE practice of shifting the stress to the penultimate syllable: "militarily" is thus sometimes rather than , and "necessarily" is in BrE either or .
"-ile".
Words ending in unstressed "-ile" derived from Latin adjectives ending "-ilis" are mostly pronounced with a full vowel in BrE but a reduced vowel or syllabic L in AmE (e.g. "fertile" rhymes with "fur tile" in BrE but with "furtle" in AmE).
AmE will (unlike BrE, except when indicated withB2) have a reduced last vowel:
In some words the pronunciation also comes into play:
Related endings "-ility", "-ilize", "-iliary" are pronounced the same in AmE as BrE.
"di-".
The pronunciation of the vowel of the prefix "di-" in words such as "dichotomy, digest" (verb), "dilate, dilemma, dilute, diluvial, dimension, direct, dissect, disyllable, divagate, diverge, diverse, divert, divest", and "divulge" as well as their derivational forms vary between and or in both British and American English.
"-ine".
The suffix "-ine", when unstressed, is pronounced sometimes (e.g. "feline"), sometimes (e.g. "morphine") and sometimes (e.g. "medicine"). Some words have variable pronunciation within BrE, or within AmE, or between BrE and AmE. Generally, AmE is more likely to favor or , and BrE to favor .
BrE , AmE (1) : "carbine"A2, "Florentine"A2, "internecine"A2, "philistine"A2, "pristine"B2, "saline"A2, "serpentine"A2.
BrE , AmE (1) (2) : "adamantine"A2.
BrE , AmE : "uterine"B2.
BrE , AmE (1) (2) (3) : "crystalline", "labyrinthine".
BrE (1) , AmE (1) (2) : "strychnine"A2.
Effects of the weak vowel merger.
The weak vowel merger causes affixes such as "-ate" (as in "climate"), "be-" (before a consonant), "de-" (as in "decide"), "-ed" (with a sounded vowel), "-es" (with a sounded vowel), "-est", "-less", "-ness", "pre-" (as in "prepare") and "re-" (before a consonant) to be pronounced with the schwa (the "a" in "about"), rather than the unstressed (found in the second syllable of "locksmith"). Conservative RP uses in each case, so that "before", "waited", "roses" and "faithless" are pronounced , rather than , which are more usual in General American. The pronunciations with are gaining ground in RP and in the case of certain suffixes (such as "-ate" and "-less") have become the predominant variants. The noun "carelessness" is pronounced in modern RP and in conservative RP; both pronunciations typically merge in GA (usually towards the latter). This variation is denoted with the symbol in some of the dictionaries published by Oxford University Press and in the "Routledge Dictionary of Pronunciation of Current English". In the latter, the British pronunciation of "climate" is transcribed , though "carelessness" is transcribed .
Affixes such as "dis-", "in-", "-ing" and "mis-" contain in conservative RP as well as General American and modern RP, so that words such as "disloyal" or "teaching" are phonemically and in all three varieties.
Weak forms.
The title "Saint" before a person's name has a weak form in BrE but not AmE:
before vowels, .
Miscellaneous pronunciation differences.
These tables list words pronounced differently but spelled the same. See also the table of words with different pronunciation reflected in the spelling.
Single differences.
Words with multiple points of difference of pronunciation are in the table after this one. Accent-based differences are ignored. For example, "Moscow" is RP and GAm , but only the – difference is highlighted here, since both the presence of a contrastive vowel in RP (which falls together with in GA) and the RP use of rather than are predictable from the accent. Also, "tiara" is listed with AmE ; the marry–merry–Mary merger changes this vowel for many Americans.
Many sources omit the length marks in transcriptions of AmE, so that words such as "father" or "keep" are transcribed and rather than and . Even though it is not phonemic, vowel length in GA works in a very similar manner to RP, so this is mainly a difference in transcription.
A2 means that American speakers may also use the British pronunciation;B2 means that British speakers may also use the American pronunciation.