What does the number "Public Law 110-42" signify?

The designation "Public Law 110-42" indicates that this is the 42nd law enacted by the 110th Congress. In the United States, laws passed by Congress are sequentially numbered within each Congress, starting from 1 for the first law passed. The first part, "110," refers to the Congress itself, which is the 110th session of Congress. The second part, "42," signifies that this is the 42nd law that has been signed into law during that congressional session.

This numbering system allows for the easy identification and reference to specific laws. Each Congress lasts for two years, and the number of laws passed can vary significantly from one Congress to another. Understanding this system is crucial for legal research and the study of legislative history, as it establishes the context in which a law was passed, including the time frame and legislative priorities during that period.