The words choir, quire sound the same but have different meanings and spellings. Why do choir, quire sound the same even though they are completely different words?
The answer is simple: choir, quire are homophones of the English language.
An organized company of singers, especially one performing church music or singing in a church.
The part of a church used by such a company of singers.
The part of the chancel in a cruciform church that is occupied by this company of singers.
A group of instruments of the same kind: a string choir.
A set of 24 or sometimes 25 sheets of paper of the same size and stock; one twentieth of a ream.
A collection of leaves of parchment or paper, folded one within the other, in a manuscript or book.
Archaic Variant of choir.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.