What name did J.R.R. Tolkien use for the central continent of his legendarium?

J.R.R. Tolkien used the name Middle-earth for the central continent of his legendarium.

Middle-earth is the setting for The Hobbit and most of The Lord of the Rings, as well as much of The Silmarillion’s later history. It is not the entire world: in Tolkien’s mythology, the wider world is called Arda, while Middle-earth is the great landmass east of the Sea.

The English term comes from older Germanic and Old English expressions, including middangeard. Tolkien adapted the idea for his mythology rather than inventing the phrase from nothing. The name refers to the inhabited lands between the divine West and the distant eastern regions.

Valinor, Númenor, and Beleriand are all important Tolkien locations, but they are not interchangeable with Middle-earth. Valinor lies in the West, Númenor is an island kingdom, and Beleriand is a region of the First Age that was later destroyed or submerged.