Flaps (or taps) and glottal stops in Standard American English (SAE) are most often found as allophonic variants of alveolar stops, although their distribution is not limited to this alone. For the purpose of this tutorial, we will focus on the former.
A flap, often referred to as “tap”[1] is defined as a voiced consonant produced with a single and brief motion in which the tip of the tongue comes into contact with the alveolar ridge.[2] Although contact may not always be exactly alveolar, it is still normally defined as such.[3]
A glottal stop is produced without the constriction of active and passive articulators, but instead with the constriction of the vocal folds to briefly obstruct all airflow. (This is the same gesture we use to hold our breath.) The glottal stop is voiceless, since the vocal folds cannot vibrate during the moment of constriction. Native speakers of SAE are sometimes unaware that this allophone exists and may mistakenly assume that there is no production of any sound when a glottal stop is used.
So let’s look at the relationship between flaps, glottal stops and alveolar stops.
An underlying /t/ surfaces as a flap [ɾ] in the phonological environment after a vocoid (vowel, glide or approximant) and before an unstressed vowel, as seen in (1):
(1) a [ˈmajɾi] ‘mighty’
b [ˈbɪɾəɹ] ‘bitter’
c [ˈbæɾəl] ‘battle’
d [ˈbaɾəm] ‘bottom’
e [ˈstæɾɪk] ‘static’
f [ˈfɔɹɾi] ‘forty’
Underlying /d/ surfaces as [ɾ] in the same environment:
(2) a [ˈspiɾi] ‘speedy’
b [ˈlawɾəɹ] ‘louder’
c [ˈfɪɾəl] ‘fiddle’
d [ˈmoɾəm] ‘modem’
e [ˈmɛɾɪk] ‘medic’
f [ˈhaɹɾəɹ] ‘harder’
To account for this distribution of flaps as allophones of alveolar stops, we posit the following rule:
(3) Flapping:
[+cor, +ant, -cont, -son] → [+cont, +son, +vce] / [-cons] __ [+syll, -cons, -stress]
i.e., {/t/,or /d/} → [ɾ] / vocoid __ unstressed vowel
In (4), we see that /t/ may surface as a glottal stop [ʔ] when preceded by a vowel or sonorant consonant, either at the end of a word (shown in 4a) or before the syllabic alveolar nasal [n̩ ] (shown in 4b-d).
(4)a [siʔ] ‘seat’
b [ˈkaʔn̩] ‘cotton’
c [ˈmawnʔn̩] ‘mountain’[4]
d [ˈkaɹʔn̩] ‘carton’
We refer to this rule as Glottal Replacement[5] or Debuccalization.
(5) Glottal Replacement:
[+cor, +ant, -cont, -son, -vce] →[-cor, -ant, -cons, +lo] / [+son] __ {#, n̩}
i.e., /t/ → [ʔ] / {vowel or sonorant C} __ {word boundary or syllabic /n/}
In some SAE dialects, /t/ is not replaced by [ʔ], but accompanied by a simultaneous or slightly preceding constriction of the glottis, known as “glottalization,” “pre-glottalization,” or “glottal reinforcement.” This is best represented with a superscripted glottal stop symbol or apostrophe: [tʔ] or [tʼ]. This may occur word finally (6a), or across word or syllable boundaries when /t/ is followed by a coronal consonant in the next syllable (6b-d).
(6) a [plejtʔ] ‘plate’
b [ˈsitʔðɛm] ‘seat them’
c [ˈlajtʔnɪŋ] ‘lightning’
d [ˈdawtʔləs] ‘doubtless’
Remember that these observations are an initial presentation of the main facts pertaining to the SAE flap and glottal stop; certain specifics may vary from dialect to dialect.
[1] The distinction was made by Peter Ladefoged but is no longer prominent in the literature, with the exception of the taxonomy of a very few languages.
[2] In other languages, the place of articulation can vary between dental, alveolar, and post-alveolar.
[3] For some speakers the point of contact is the upper front teeth, in which case the dental diacritic may be added beneath the symbol for the flap if such precision is called for: [ɾ̪].
[4] For some speakers, the preceding /n/ in this word is deleted, giving the pronunciation [ˈmawʔn̩].
[5] “Glottalization” is a misnomer, because that technically describes the addition of the feature [+constr] without losing the oral place of articulation, as in many British dialects for voiceless stops of any place of articulation.
Aronow & McHugh 2016
