quenya_grammar1-2  Exercise 2: The Diaeresis and the Diphthongs
===============================================================

The diaeresis (ë) marks a vowel that is not part of a diphthong:
  - in "ëa" the e and a are two separate vowels, not one diphthong
  - in "lassë" it shows that the final e is pronounced (las-së), not silent

Six diphthongs of late Noldorin Quenya: iu, eu, ai, au, oi, ui.
Only "iu" is rising (it sounds like "yu"); the other five are falling.