“Deësis” is an example of “diæresis.” That is, the two dots over the second “e” in “deësis” form a diacritical mark indicating that the second “e” is to be pronounced separately from the first. “Deësis,” from the Greek δέηοις (“prayer”), refers to any art work depicting Christ enthroned, with the Virgin on one side and St. John on the other. According to A.C. Bliss, writing in A Dictionary of Foreign Words & Phrases in Current English, referring to a diæresis as an umlaut “is to be deprecated,” so please feel free to do so.
