S IS FOR SE-TENANT
Se-tenant is the French term for "joined together." In philately, it refers to two or more adjacent stamps having different designs, denominations, or colors.
Once rare, this has become the most popular format for U.S. stamps.
Some sheets feature alternating designs; on others, each stamp on the sheet is a unique design.
There have even been several 50-stamp sheets showcasing an aspect of each state.