The English language contains many words containing a letter 'tee' surrounded on either side by a vowel. There are also many words that end with a 'tee'. But we don't all always pronounce quite all of those 'tees', do we? It is quite common for an average native-speaker of British English to drop the final 'tee' of a word like 'nut' or 'bolt'. In garages and offices all over the country, those words will be pronounced without a trace of a 'tee' to be heard, and perfectly understood. Some regional accents go further, and when saying the word butter, for instance, might 'drop' the intervocalic 'tee' and say something rather like bu'ah.
Now, those 'dropped tees' aren't replaced by any other letter, but neither is there nothing left at all. They are replaced with a 'sound' that is produced by native-speakers of Brit English dozens, hundreds or even, yes, in some cases thousands of times a day. In other languages this 'sound' is recognised as an important part of the language. Yet very few people know what it's called. Well, it's called a glottal stop, and it's great!
A glo[?]al wha[?]?
A glottal stop is a sound articulated by humans and used in many languages around the world as a phoneme1. It can be described in phonetics as 'a momentary check on the airstream caused by closing the gap between the vocal chords'. The aperture at the top of the vocal chords is called the glottis and when it closes tight the chords stop vibrating, creating a brief silence, then a slight choke or cough-like explosive sound upon release. In linguistics, this is called a glottal stop and it can be transcribed as [?].
The glottal stop does function as a phoneme in its own right in numerous other languages around the world, though, including Arabic and many African and American-Indian languages. The process of momentary partial or complete closure of the glottis is known as glottalisation. The closure may occur before during or after the articulation producing glottalised stops and sibilants as well as glottalised vowels.
Glottalisation in the UK
The glottal stop is not considered a separate phoneme of RP English2, but in some dialects it certainly is used as an allophone3 of the RP voiceless plosive /t/. Thus the common Estuary English pronunciations 'play' (although the 'y' sound is not pronounced) and 'bo'ull' for RP 'plate' and 'bottle'. Phonetically these four utterances could be annotated /pla?/ vs /plat/ and /bo?'l/ vs /bot'l/.
Although 'dropping your tees', rather like dropping your 'aitches', is generally regarded to be 'bad' pronunciation, in informal speech even the purest RP speaker will often replace a final 'tee' with a glottal stop. Indeed, it is probably fair to say that most people would consider pronouncing every last 'tee' to be 'overdoing it'. Even then, an utterance such as 'Oh-oh!', said as a warning that the speaker has thought of something bad, is correctly pronounced with a glottal stop between the end of the first 'oh' and the beginning of the second 'oh'.
Compare and Contrast
Be'y bough' a bi' of bu'er.
Bu' the bi' of bu'er Be'y bough' was bi'er,
So Be'y bough' anuvver bi' of bu'er.
Betty bought a bit of butter.
But the bit of butter Betty bought was bitter,
So Betty bought another bit of butter.