How does American English differ from British English?

Characteristics of American English

Standard American English

The pronunciation of this book is based on American English. There are of course many dialects in America, and the one that is viewed as the standard accent, or general English, is the accent spoken by the Midwest region of America (e.g., Ohio and Indiana). This accent is viewed as standard because it lacks the coloring of any regionality. In other words, people can easily tell which region of America you are from if you speak with the Boston accent, the Southern accent or the Minnesota accent, but they cannot tell which region of America you are from if you speak with the accent of the Midwesterners. This neutrality from regionality was the reason that the accent was chosen for the accent of mass media. So, by American English, we mean the accent adopted by American mass media. 

Summary: Standard American English lacks any regional characteristics, so it is used on TV and radio. In America, people who live in the Midwest speak standard American English.

American English vs British English

The father-bother merger

There are many differences between American English and British English. For one, American English has fewer vowel sounds than British English since some British vowel phonemes are merged into one in American English. For example, the British back open rounded vowel /ɒ/ does not exist in American English. In Britain, words like ‘hot, stop, cloth, are all pronounced with /ɒ/ sound. In America, they are all pronounced with the /ɑ/ sound. This phenomenon is called the father-bother merger since in British English,‘father’ and ‘bother’ have different vowel sounds: /fɑːðə/ and /bɒðə/. But in the US, both are pronounced with /ɑ/ sound /fɑðər/ and /bɑðər/.

Summary: In America, the British /ɒ/ is pronounced with /ɑ/ sound.

The cot–caught  merger

Pushing the merger further, in American English, many words that used to be pronounced with /ɔ/ are pronounced with /ɑ/. This phenomenon is called the cot–caught merger. Areas in the US where there is no-merger, ‘cot’ and ‘caught’ are pronounced as /kɑt/ and /kɔt/. But in standard American english, they sound the same, /kɑt/. 

Summary: In Standard American English, words that used to be pronounced with the pure /ɔ/ vowel sound are pronounced with /ɑ/ sound.

Vowel shift

There is also the vowel shift in American English. The most salient one is the shift from /a:/ to /æ/. In Britain, words like “aunt, bath, laugh, class, chance, ask” are all spoken with the /ɑ:/ sound. In America, however, they are all pronounced with the /æ/ sound: “aunt, bath, laugh, class, chance, ask.”

Summary: Many words that are pronounced with /ɑ/ in England are pronounced with /æ/ in America. 

Rhotic accent (r-colored vowels)

The most salient difference between American English and British English should be relating to the pronunciation of the R sound. In America, R is always pronounced whenever there is an R in the spelling. British people, however, pronounce R only when it is the beginning sound in a syllable. If R occurs after a vowel in a syllable, R is not pronounced. So for instance, British people will pronounce R in rice, ramen, and bright, but they will not pronounce R in ear, car and butter.” In American English, however, R is pronounced regardless of its position. For this reason, American English is called the rhotic accent. The word ‘rhotic’ comes from the Greek letter ‘rho’ as Greek letters are often used for the phonetic purpose. Due to the pronunciation of the R after a vowel, the vowel sound that precedes an R has some coloring of R. Such a vowel is called an R-colored vowel or R-controlled vowel, which is unique in American English.

Summary: British people do not pronounce /r/ if 'r' occurs after a vowel in a syllable. Americans pronounce /r/ whether 'r' occurs before or after a vowel. To indicate this difference, British English is called the non-rhotc accent, and American English is called the rhotic accent. The "vowel + r" sound is called the r-colored vowel. Non-American-English natives say that pronouncing r-colored vowels feels like swallowing the tongue.

Vowel length, a prosodic feature

Another difference between them is the nature of vowel length. In British English, each vowel is viewed as either a long vowel or a short vowel, but in American English vowel length is viewed as a prosodic feature, not a phonemic feature. That is, the length of a vowel sound is not viewed as an intrinsic feature of vowel phoneme sounds. Rather, how long we should hold the vowel sound is determined by such factors as whether the stress lies on the vowel or not and whether it is followed by a voiced sound or not. If the vowel is stressed or if it is followed by a voiced sound, the vowel sound becomes long. 

Summary: In British English, each vowel is classified as either a long vowel or a short vowel. In American English, vowel length is determined by surrounding sounds. Vowels that receive stress or vowels followed by voiced sounds are long.

Flap T, [ɾ]

There are also sounds that are uniquely American. The most salient one is the flap T, which is an allophone of ‘t’ and ‘d’. The sound is made by the tongue briefly tapping the alveolar ridge. When this happens, ‘t’ and ‘d’ are pronounced as a sound somewhere between /r/ and /l/.

Summary: One reason that American English sounds smoother than British English is that Americans do not use the phonetic /t/ or /d/ sound (called the alveolar stop). Instead, they use an allophone of /t/ or /d/, called flap t, whose IPA symbol is [ɾ].

Yod dropping

Americans also pronounce some words differently from British people. The most notable one is the phenomenon of yod dropping, where the /j/ sound is dropped after alveolar consonants like /n, t, d, s, z/. So, while British people pronounce ‘news’ and ‘tune’ with /ju/ sound, American people pronounce them with the /u/ sound. By the way, this phenomenon is called yod-dropping since the /j/ sound is called yod in Hebrew.

Summary: Many words which British people pronounce with /ju/ sound are pronounced with /u/ by Americans.