The power to "veto" a bill is actually only held by the president. Once both the House of Representatives and the Senate approves a bill (by a two-thirds majority), it is sent to the president to be looked over. Once he reads it, he can either decide to approve it and make it an official law, or he can veto it, and it goes back to the House and Senate, where they either decide to revise it and revote on it, or they trash it completely.
2/3 or 66%.
2/3
the President
2/3 vote from each house
Fifty one in the Senate and 218 in the House.
When each house of congress passes a different version of a bill and those differences must be resolved.
2/3 vote from each house is needed to override a veto.
a conference committee
After a bill is introduced in either the House or the Senate, the bill is assigned a number.
The legislative process requires both the Senate and the House of Representatives to approve a bill to become a law. Each house must vote on the bill and a simple majority vote is required.
House of Representatives
The term is not writing, but overriding. Both the House and Senate must approve a vetoed bill by a 2/3rds majority.
Most bills start in committees. A bill that passes committee is then voted on in the full house or senate. A bill must pass the house and the senate, and then it goes to the president.
After a bill is introduced in either the House or the Senate, the bill is assigned a number.