Glottal stop /ʔ/

 

Silent T

Some spelling combinations almost always produce a silent t. These are examples:

“-ften”: 

often, soften

“-sten”: 

listen, glisten, hasten, fasten, moisten, christen, chasten

“-stle”: 

castle, nestle, pestle, apostle, thistle, whistle, wrestle, gristle

‘T’ can also be silent in a consonant cluster when it comes in the middle of the cluster. For example, 

lastly, postman, coastguard, wristband

When ‘n’ comes before ‘t’ and a vowel follows after ‘t,’ the /t/ sound can disappear, and we hear only the /n/ sound. That is, the combination /nt/ might be pronounced as /n/. For this reason, ‘winter’ and ‘winner’ become homophones. These are examples where ‘t’ is silent after ‘n’ 

Center, wanted, interview, international, advantage percentage 

Glottal stop /ʔ/

Another allophone of /t/ is a glottal stop, represented by this symbol, /Ɂ/. It is the sound when we say “uh-oh.” The middle choking sound is the glottal stop. The glottal stop occurs when the vocal folds are briefly closed, and then released. When /t/ is expressed in a glottal stop, there is no sound for /t/. 

Before syllabic N

In American English, glottal stop happens mainly when ‘t’ comes before the syllabic N. In other words, the glottal stop occurs before an unstressed “un” sound (/ən/). These words have a glottal stop.

beaten, bitten, Britain, button, certain, Clinton, cotton, curtain, eaten, gotten, forgotten, fountain, kitten, Latin, mitten, rotten, satin, written, mountain, sentence Marten, shorten, important

The glottal stop can also occur when ‘t’ comes between an r-colored vowel and n. For example, 

Partner, kindergartner, smartness, expertness, shortness