Other/the other/another...

[Tortoise]

I don't know where we use other, the other, another. Please help me.
For example, in this sentence what words do you use:

I have 2 letters._______ is from my mother.______ is from my friend.

Also, in class, the teacher asks the monitor "Who's absent today?". What is the best way to reply if there's no one is absent? Is "No one" formal?

[Alan]

Hi Tortoise,

The missing words are: one is from my mother and the other is from my friend.
In answer to the teacher you could say: No-one or nobody.

Alan
_________________
English as a Second Language
You can read my ESL story Present Simple

[Sidle Jinks]

Hi!

[Alan]

Hi Sidle Jinks,

Both forms are all right - you can choose either.

Alan
_________________
English as a Foreign Language
You can read my EFL story Progressive Forms

[Sidle Jinks]

Thank you very much, Alan, for your explanation!
_________________
Factum non fabula

[Tortoise]

Hi!
But when we use "another" instead of "the other", Sir Alan?

Thanks.

[Alan]

Hi tortoise,

Another means A different/additional one and the other means THE different/additional one. Have a look at what I've written on the articles a/an/the on this site:

esl lessons

the' vs. 'a/an'

Alan
_________________
English as a Second Language
You can read my ESL story Passive Voice