9.3.1 Distribution of glottally reinforced and glottaled stops

Glottalization

Glottalization affects unisyllabic GA /p,t,k/ in the coda, if preceded by a voiced sound. Below are some examples.

Glottalization before p

cap – /kæp/

Also

cops

harpsichord

helped

campsite

Glottalization before t

cat – /kæt/

Also

cart

atlas

can’t

halts

Glottalization before k

lick – /lɪk/

Also

sacked

bark

tanks

huckster

No Glottalization

Glottalization is absent when there is no voiced sound preceding /p,t,k/, and when /p,t,k/ are ambisyllabic.

No Glottalization before p

lisp – /lɪsp/

No Glottalization before t

best – /bɛst/

Also

opt

No Glottalization before k

mask – /mæsk/

Ambisyllabic p

April – /ˈeɪprəl/

Also

apple

ample

corporal

Ambisyllabic t

mattress – /ˈmætrəs/

Also

metal

central

Santa

Ambisyllabic k

orchid – /ˈɔrkɪd/

Also

buckle

Berkeley

uncle

Glottaling

Glottaling of GA /t/ may be viewed as a variable extension of glottalization. The rules have comparable environments, except that glottaling only affects GA /t/, and /t/ must be final in its coda.
It may therefore apply in cat, cart, felt, resentment, or atlas.

atlas – /ˈætləs/

It does not, however, apply in cap, cats, eighth, or central.

central – /ˈsɛntrəl/

Special mention must be made of /t/ before syllabic /n/, as in cotton, buttoned, which, though ambisyllabic, is always replaced with [ʔ]:

cotton – [kɑːʔn̩]

buttoned – [bʌʔn̩d]

American English Phonetics

Another American English Faculty Project