Rules for inanimate objects and possessives
An inanimate object is incapable of possession. Therefore, nouns referring to inanimate objects should be possessive. Instead, use a prepositional phrase to express relationship.
the bottom of the barrel (NOT: the barrel's bottom)
the wording of the agreement (NOT: the agreement's wording)
the lower level of the hospital (NOT: the hospital's lower level)
In many common expressions, such as slang terms, the possessive form has come to be accepted usage.
cat's meow
the earth's atmosophere
stone's throw
for heaven's sake
at arm's length
Possessive phrases that refer to time, measurement or money have become accepted in usage, as well.
one day's notice
two days' notice
several dollars' worth
two years' progress
this morning's news
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