In linguistics, diaeresis, or dieresis,'s the pronunciation of two adjacent vowels in two separate syllables rather than as a diphthong, and it's also the name of the diacritic mark (¨ ) used to prompt the reader to pronounce adjacent vowels in this manner. The word dieresis comes from the Greek noun διαίρεσις (diaíresis, "division," or literally, "choice between"), which derives from the verb διαιρεῖ_… (More on Diaresis)