a or t he

[keitra]

Which is correct?

This is (a, the)letter that I have written, just a moment ago, to the President.

[Claud.Butler]

"This is the letter..." seems correct.

[jno]

If you'd already mentioned it you could say 'the letter' (ie the letter you'd just talked about); if it was the first time you'd brought it up, 'a letter' would be better.

[another-view]

Both of these are correct.

[another-view]

"The" is used for a definite item. "A" could be one of many.

For example, "this is the lady I married" implies you only have one wife, whereas "this is A lady I married" implies you have had more than one wife.

[wakeover]

Totally agree with another-view