The Hebrew word is shabuwa' which means "sevens" (used the way we use dozen). In this case it is a "week of years".
70 "weeks of years" are determined upon "thy people and thy holy city" (Jerusalem). This key prophecy is from vs. 24-27.
Jesus makes reference to this prophecy twice: Matt 24:15 and Mark 13:14. The "abomination of desolation" takes place in the Most Holy Place.