A bill filed in one chamber that is identical or very similar to a bill filed in the opposite chamber. Companion bills are used to expedite passage, as they provide a means for committee consideration of a measure to occur in both chambers simultaneously. A companion bill that has passed one chamber can then be substituted for the companion bill in the opposite chamber.

[Source: Texas Legislative Glossary: Texas Legislative Council for the 85th Legislature, Prepared by the Research Division of the Texas Legislative Council]