I have forgotten/I forgot
Hello there. I want to know if I can say "I forgot" with no time expressions?
Here's some context:
My teacher: "show me that you have done your homework" and me: "sorry I forgot it".
and here's another:
I've just arrived at school and I meet my friend. He says "hey have you brought the documents?" and me "OMG I have forgotten them, sorry (I haven't even thought about them before)"
Is it correct in this situation?
Thank you :)

Question

I have forgotten/I forgot
Hello there. I want to know if I can say "I forgot" with no time expressions? 
Here's some context:
My teacher: "show me that you have done your homework" and me: "sorry I forgot it".
and here's another:
I've just arrived at school and I meet my friend. He says "hey have you brought the documents?" and me "OMG I have forgotten them, sorry (I haven't even thought about them before)"
Is it correct in this situation? 
Thank you :)

Answer

Yes. You've used this the the right context. Well done:)

Answer

In conversational English, you can use either when there is just one past situation and the time is unspecified. You can either think of it as before now but relevant to now (present perfect) or finished in the past (past simple).

Не упустите возможность выучить язык, не выходя из дома. Ознакомьтесь с подборкой опытных преподавателей и запишитесь на свой первый урок прямо сейчас!