Frequency: The word is one of the 3000 most common words in English.
Note: 'Yours' is the second person possessive pronoun. 'Yours' can refer to one or more people.
1.
A speaker or writer uses yours to refer to something that belongs or relates to the person or people that they are talking or writing to.
I'll take my coat upstairs. Shall I take yours, Roberta?...
I believe Paul was a friend of yours...
If yours is a high-stress job, it is important that you learn how to cope.
PRON
2.
People write yours, yours sincerely, or yours faithfully at the end of a letter before they sign their name.
With best regards, Yours, George...
Yours faithfully, Michael Moore, London Business School...
CONVENTION