Does Doubleheader Have a Hyphen?

The Free Dictionary has an entry for doubleheader and double-header and no entry for singleheader or single-header. Logic does not always apply to related words when the base word has been adopted because of frequent use. I would accept the dictionary entry and use two words, single header, no hyphen.

Is doubleheader one word or two words?

Sports. two games, as of baseball, between the same teams on the same day in immediate succession. two games, as of basketball, between two different pairs of teams on the same day in immediate succession.

What doubleheader means?

1 : a train pulled by two locomotives. 2 : two games, contests, or events held consecutively on the same program.