This is the 2733rd most frequent Russian word.
документ
A document.
The word 'документ' refers to a specific document, perhaps an ID or an official paper, that the speaker accidentally left at home.
Я забыл свой документ дома.
I forgot my document at home.
The word 'документы' is used in its plural form, referring to several documents, indicating a requirement or obligation to complete them.
Документы должны быть подписаны до завтра.
The documents need to be signed by tomorrow.
The word 'документ' is used to refer to an old piece of writing or record, serving as evidence or historical material.