determiner , pronoun
1) (in telling time) ~ past the hour (it's ~ past four)
2) ~ of (~ of them)
3) ( misc. ) it's not ~ bad ('it's fairly good')
USAGE NOTE: The use of the preposition of is necessary when a pronoun follows. When a noun follows, the of may be omitted- ~ (of) the students; ~ (of) the audience . However, compare-- she spent ~ (of) the money; she spent her ~ of the money . Note the constructions- a ~ hour, ~ an hour .