Video notes

The glottal stop is a feature of English and many other languages. In English it is often used in place of the letter 't', but can be used in other situations as well.

Why is it called a 'glottal stop'? 

Because you stop the air flowing through the glottis in your throat.

What is the glottis?

It's the opening between the vocal folds. The vocal folds or cords can open or close to let air through or stop the air.

In between the uh oh -
We don't say ahhhooo

The little stop in between the two words is called a glottal stop.

It's very common to clear the glottal t, in both formal and informal English. You will also hear glottal p and k in words like clockwork, background and clipboard, but we are mainly talking about t in this video.

The 'glottal t'

In formal English, the glottal t is usually used before a consonant sound (often l, m or n).

setback
fitness
witness
Scotland

A lot of 't' sounds at the end of words can also change to a glottal stop, especially when you have l, m or n + t - for example in can't, want and late.

You have to pronounce the t at the beginning of the word - for example in 'today'.

At the end of the day.
He told me that he was coming.
It's not hot in winter.
I'm fine. What about you?
I want to, but I can't
The cat sat on the mat.
I can't hear you.
It's difficult to say.
I felt happy yesterday.

When there is a vowel before and after the 't' sound, we would normally pronounce the 'T'. But in some British accents and informal ways of speaking people, people might use a glottal stop in this case.  

Britain
water
better
butter
bottle
button

In American English, these would be pronounced with a tapped 't' on your alveolar ridge, but this isn't used much in the British accent.