Ever thought about the ends of these words?
'-tain' may not be as simple as you think.
What about 'captain', 'mountain' and 'fountain'?
They are different to 'certain' and 'curtain'.
Which are different again to words like 'contain' and 'sustain'.
And are you using your own language as a reference?
It's what a Turkish client of mine was doing. The word 'captain' in Turkish is 'captan'. She was using the pronunciation of the vowels in the Turkish word in the English word - which seldom works!
Watch the video above to correct your pronunciation of '-tain' word ending.