I think it would be very usefel for myself and other beginners if someone could tell us a bit about linguistic terms peculiar to Icelandic/Old Norse, please.
To start the ball rolling:
In Colloquial Icelandic (the book I use), the author mentions something she calls fractION (e.g. jökul + i = jökli]]. In Glendening's Teach Yourself Icelandic, he talks of fractURE, which he translates as klofning, citing the masc. noun fjörður - fjarðar - firðir (acc. to Glendening from original root ferð). My instinct would be that they are actually quite separate phenomena: klofning seems a good description only of the second phenomenon just mentioned, as the original E "splits" into 2 bits, to wit the J and the Ö/A, and the first meaning of KLOFNA in Hólmarsson is given as TO SPLIT.
Do Icelanders call both of these phenomena KLOFNING? I.e. do you use it BOTH for jökul becoming jökli rather than jökuli and for the vowel changes in fjörður - fjarðar - firðir?