When it comes to choosing medieval or mediaeval, it has been commonly observed people in Great Britain were more willing to use the ae, while Americans preferred just using the e. Perhaps this was true, but even the British gradually shifted to medieval.

By the middle of the twentieth century it was clear that medieval would be the common spelling. This was not an inevitable outcome, for archaeology remains far more popular than archeology. However, it seems that the word mediaeval will not be making a comeback. Only a handful of books published in recent years use that term.

There are a few places where the word mediaeval endures. For example, the University of Toronto has both a Centre of Medieval Studies and a Pontifical Institute of Mediaeval Studies, so perhaps the older form will live on.