65 ILCS 5/6-4-2
All ordinances passed by the council shall be deposited with the city or village clerk. If the mayor approves of them, he shall sign them. Those of which he disapproves he shall return to the council, with his written objections, at the next regular meeting of the council occurring not less than 5 days after their passage. The mayor may disapprove of any one or more sums appropriated in any ordinance, resolution, or motion making an appropriation, and, if so, the remainder shall be effective. However, the mayor may disapprove entirely of an ordinance, resolution, or motion making an appropriation. If the mayor fails to return any ordinance or any specified resolution or motion with his written objections, within the designated time, it shall become effective despite the absence of his signature. The vote on every ordinance shall be by yeas and nays, and shall be recorded in the journal.
65 ILCS 5/6-4-2