Important Things to Know
The University of Hawaii at Hilo College of Hawaiian Language recommends one word, "Maunakea" as the proper Hawaiian usage. Maunakea is a proper noun—the name of the mountain on the Island of Hawaii. "Mauna Kea" spelled as two words is really referring to any white mountain—it is a common noun (vs. the proper noun).
The one word version is also specific to the "Mountain of Wakea," the proper name of this mountain as addressed in the Kumulipo Chant of Creation and throughout ‘Imiloa's exhibits.
Another example of a common noun to a proper noun is ka pua. Spelled separately it refers to "the flower" or any flower. Spelled as Kapua, it refers to the "proper name" of someone/something.
For more information, visit the `Imiloa website.