The fifty-first runner crossed the finish line, exhausted but proud.

They cut the cake into fifty-one equal slices, and she happily took the fifty-first.

At the reunion, they told stories about the fifty-firsts of their graduating classes, who had all come back to visit.

After the government signed a military pact with the United States, critics called the small island nation the fifty-first state.

Some politicians still debate which territories could become the fifty-first states.