Flapping

[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.

[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].

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].

Some linguists consider it obligatory for most American dialects to flap /t/ between a stressed and an unstressed vowel.

[22] In North American English, [t] and [ʔ] (t-glottalization) were the only realizations of /t/ before /ən/,[23] but studies in the 2020s have found [ɾ] in younger US speakers.

[24] 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]),[26][27] 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.

[7] Nevertheless, Vaux (2000) postulates that it applies to alveolar stops: 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]).

[34][35] 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.

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.

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.

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 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].