Flapping or tapping, also known as alveolar flapping, intervocalic flapping, or t-voicing, is a phonological process involving a voiced alveolar tap or flap; it is found in many varieties of English, especially North American, Cardiff, Ulster, Australian and New Zealand English, where the voiceless alveolar stop consonant phoneme /t/ is pronounced as a voiced alveolar flap [ɾ], a sound produced by briefly tapping the alveolar ridge with the tongue, when placed between vowels. In London English, the flapped [ɾ] is perceived as a casual pronunciation intermediate between the "posh" affricate [tsʰ] and the "rough" glottal stop [ʔ].^[1] In some varieties, /d/, the voiced counterpart of /t/, may also be frequently pronounced as a flap in such positions, making pairs of words like latter and ladder sound similar or identical. In similar positions, the combination /nt/ may be pronounced as a nasalized flap [ɾ̃], making winter sound similar or identical to winner.

Flapping of /t/ is sometimes perceived as the replacement of /t/ with /d/; for example, the word butter pronounced with flapping may be heard as "budder".^[2]

In other dialects of English, such as South African English, Scottish English, some Northern England English (like Scouse), and older varieties of Received Pronunciation, the flap is a variant of /r/ (see Pronunciation of English /r/).^[3]

Terminology and articulation

The terms flap and tap are often used synonymously, although some authors make a distinction between them. When the distinction is made, a flap involves a rapid backward and forward movement of the tongue tip, while a tap involves an upward and downward movement.^[4] Linguists disagree on whether the sound produced in the present process is a flap or a tap, and by extension on whether the process is better called flapping or tapping,^[5] while flapping has traditionally been more widely used.^[6][7] Derrick & Gick (2011) identify four types of sounds produced in the process: alveolar tap, down-flap, up-flap, and postalveolar tap (found in autumn, Berta, otter, and murder, respectively).^[8]

In Cockney, another voiced variant of /t/ that has been reported to occur to coexist with the alveolar tap (and other allophones, such as the very common glottal stop) is a simple voiced alveolar stop [d], which occurs especially in the words little [ˈlɪdʊ], hospital [ˈɒspɪdʊ] and whatever [wɒˈdɛvə]. That too results in a (variable) merger with /d/, whereas the tap does not.^[9]

In Cardiff English, the alveolar tap is less rapid than the corresponding sound in traditional RP, being more similar to /d/. It also involves a larger part of the tongue. Thus, the typical Cardiff pronunciation of hospital as [ˈɑspɪɾl̩] or [ˈɑspɪɾʊ] is quite similar to Cockney [ˈɒspɪdʊ], though it does not involve a neutralization of the flap with [d].^[10]

Distribution

Pronunciation of latter and ladder with and without flapping

[ˈlætɚ ˈlædɚ ˈlæɾɚ]

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Pronunciation of winter and winner with and without flapping

[ˈwɪntɚ ˈwɪnɚ ˈwɪɾ̃ɚ]

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Pronunciation of seventy with and without t-voicing, and with flapping

[ˈsɛvn̩ti ˈsɛvn̩di ˈsɛvɨɾ̃i]

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Flapping of /t/ and /d/ is a prominent feature of North American English. Some linguists consider it obligatory for most American dialects to flap /t/ between a stressed and an unstressed vowel.^[7][11] Flapping of /t/ also occurs in Australian, New Zealand and (especially Northern) Irish English, and more infrequently or variably in South African English, Cockney, and Received Pronunciation.^[12][13][14]

The exact conditions for flapping in North American English are unknown, although it is widely understood that it occurs in an alveolar stop, /t/ or /d/, when placed between two vowels, provided the second vowel is unstressed (as in butter, writing, wedding, loader).^[6][15] Across word boundaries, however, it can occur between any two vowels, provided the second vowel begins a word (as in get over [ɡɛɾˈoʊvɚ]).^[6][15] This extends to morphological boundaries within compound words (as in whatever [ˌwʌɾˈɛvɚ]).^[16] In addition to vowels, segments that may precede the flap include /r/ (as in party)^[11][17] and occasionally /l/ (as in faulty).^[18][19] Flapping after /l/ is more common in Canadian English than in American English.^[20] Syllabic /l/ may also follow the flap (as in bottle).^[21] Flapping of /t/ before syllabic /n/ (as in button) is observed in Australian English,^[22] while [t] (with nasal release) and [ʔ] (t-glottalization) are the only possibilities in North American English.^[23]

Morpheme-internally, the vowel following the flap must not only be unstressed but also be a reduced one (namely /ə/, morpheme-final or prevocalic /i, oʊ/, or /ɪ/ preceding /ŋ/, /k/, etc.^[a]),^[25][26] so words like botox, retail, and latex are not flapped in spite of the primary stress on the first syllables,^[11] while pity, motto, and Keating can be.^[25] The second syllables in the former set of words can thus be considered as having secondary stress.^[6]

Word-medial flapping is also prohibited in foot-initial positions. This prevents words such as militaristic, spirantization, and Mediterranean from flapping, despite capitalistic and alphabetization, for example, being flapped. This is known as the Withgott effect.^[27][28]

In North American English, the cluster /nt/ (but not /nd/) in the same environment as flapped /t/ may be realized as a nasal flap [ɾ̃]. Intervocalic /n/ is also often realized as a nasal flap, so words like winter and winner can become homophonous.^[29] According to Wells (1982), in the United States, Southerners tend to pronounce winter and winner identically, while Northerners, especially those from the east coast, tend to retain the distinction, pronouncing winter with [ɾ̃] or [nt] and winner with [n].^[30]

Given these intricacies, it is difficult to formulate a phonological rule that accurately predicts flapping.^[7] Nevertheless, Vaux (2000) postulates that it applies to alveolar stops:

• after a sonorant other than l, m, or ŋ, but with restrictions on n;
• before an unstressed vowel within words, or before any vowel across a word boundary;
• when not in foot-initial position.^[31]

Exceptions include the preposition/particle to and words derived from it, such as today, tonight, tomorrow, and together, wherein /t/ may be flapped when intervocalic (as in go to sleep [ˌɡoʊɾəˈslip]).^[32] In Australian English, numerals thirteen, fourteen, and eighteen are often flapped despite the second vowel being stressed.^[33][34] In a handful of words such as seventy, ninety, and carpenter, /nt/ is frequently pronounced as [nd], retaining /n/ and voicing /t/, although it may still become [ɾ̃] in rapid speech.^[35][36]

Homophony

Flapping is a specific type of lenition, specifically intervocalic weakening. It leads to the neutralization of the distinction between /t/ and /d/ in appropriate environments, a partial merger of the two phonemes, provided that both /t/ and /d/ are flapped.^[5][37] Some speakers, however, flap only /t/ but not /d/. Yet, for a minority of speakers, the merger can occur only if neither sound is flapped. That is the case in Cockney, where /t/ is occasionally voiced to [d], yielding a variable merger of little and Lidl.^[38] For speakers with the merger, the following utterances sound the same or almost the same:

In accents characterized by Canadian raising, such words as riding and writing may be flapped yet still distinguished by the quality of the vowel: riding [ˈɹaɪɾɪŋ], writing [ˈɹʌɪɾɪŋ].^[39] Vowel duration may also be different, with a longer vowel before /d/ than before /t/, due to pre-fortis clipping.^[40]

Withgott effect

In a dissertation in 1982, M.M. Withgott demonstrated that, among speakers of American English, words seem to be chunked into pronunciation units she referred to as a foot, similar to a metrical unit in poetry. Such chunking was said to block flapping in the word ‘Mediterranean’ ([[Medi[terranean] ], cf. [ [sub[terranean]]). How a word is chunked relates to its morphological derivation, as seen by contrasting morphologically similar pairs such as the following (where the vertical bar shows where Withgott argued there is boundary between neighboring feet):

The medial t in càpitalístic can be flapped as easily as in post-stress cátty [ˈkʰæɾi], in contrast to the medial t in mìlitarístic, which comes at the beginning of a foot, and so must be pronounced as [tʰ], like a t at the beginning of a word.

Long, seemingly monomorphemic words also are chunked in English for purposes of pronunciation. In such words [t]’s — as well as the other unvoiced stops — are pronounced like initial segments whenever they receive secondary stress or are at the beginning of a foot:

Navra tilóva

Abra cadábra

Ala kazám

Rázz matàzz

But:

Fliberti gibety

Humu humu nuku nuku apu a‘a

T-to-R rule

The origins of the T-to-R rule lie in the flapping of /t/ and the subsequent reinterpretation of the flap as /r/, which was then followed by the use of the prevailing variant of /r/, namely the approximant [ɹ]. It is applied in Northern England English and it is always stigmatized. The application of that rule means that shut in the phrasal verb to shut up /ʃʊrˈʊp/ has a different phonemic form than the citation form of the verb to shut /ʃʊt/. The rule is typically not applied in the word-internal position.^[41]

The T-to-R rule has also been reported to occur in the Cardiff dialect (where the merged consonant can surface as either an approximant or a flap) and South African English (where only a flap is possible). In the Cardiff dialect, the rule is typically applied between any vowel (including long vowels) and /ə/ or the reduced /ɪ/ (also across word boundaries), so that starting /ˈstaːtɪŋ/ and starring /ˈstaːrɪŋ/ can be homophonous as [ˈstaːɹɪn ~ ˈstaːɾɪn]. In South African English, the merger is possible only for those speakers who use the flapped allophone of /r/ (making the starting–starring minimal pair homophonous as [ˈstɑːɾɪŋ]), otherwise the sounds are distinguished as a flap (or a voiceless stop) for /t/ ([ˈstɑːɾɪŋ ~ stɑːtɪŋ]) vs. approximant for /r/ ([ˈstɑːɹɪŋ]). There, the merger occurs word-internally between vowels in those environments where flapping is possible in North American English.^[42][43]