which's

Pronoun

 * 1)  Of which; alternative to inanimate sense of “whose”.
 * 2) Of or pertaining to [some noun phrase ending with] which.
 * 3) * 1899, Minisink Valley Historical Society, Collections, Connecticut Historical Society, page 86:
 * Whereas we are informed that the small pox prevails at New York, Connecticut, &c, the preventing of which’s coming into this place is of the utmost consequence, all persons are hereby notified that orders are given by us for all vessells coming into this port to hoist a jack at the main topmast head,
 * Whereas we are informed that the small pox prevails at New York, Connecticut, &c, the preventing of which’s coming into this place is of the utmost consequence, all persons are hereby notified that orders are given by us for all vessells coming into this port to hoist a jack at the main topmast head,

Usage notes
In the inanimate “of which” sense, arises out of doubt about whether  can be used with an inanimate antecedent. In standard English, is the possessive of form of both  and, so  is appropriate for such antecedents.

In the noun-phrase-final sense, is best analyzed not as a single word, but as the last word of a noun phrase, the whole phrase to which  is appended. In this sense, changing to  is hypercorrection.

Synonyms

 * which, whose

Etymology 2
From +.

Contraction

 * I didn’t ask for installation but they still charge me the installation which’s fine for me.
 * 1) * 1922, Marion Ames Taggart, Who is Sylvia?, Page & Company Doubleday, Country Life Press, page 267:
 * He’s the one that gits the full good ’f a clock, which’s the comp’ny they are.
 * 1) * 1922, Marion Ames Taggart, Who is Sylvia?, Page & Company Doubleday, Country Life Press, page 267:
 * He’s the one that gits the full good ’f a clock, which’s the comp’ny they are.