| Assimilation | A process in which a sound becomes more like a nearby sound in either manner or place of articulation |
| Elision | The omission of a sound from a word or utterance |
| Fortition | The hardening of a sound. Used in our context to refer to the development of a fricative into a stop, e.g. ð > d in brennði > brenndi |
| Front mutation | A process in which a back vowel shifted forward to become the directly corresponding front vowel under influence from an /i/ or /j/ in the following syllable |
| Labial mutation | A process in which an unrounded vowel receives liprounding under the influence of an /u/ or /w/ in the following syllable. The only visible effect of this within Old Norse paradigms is the alternation between a (unrounded) and ǫ (rounded), as in kalla, kǫlluðu. |
| Principle of minimal effort | A governing principle of language change, leading speakers to expend the minimum effort required for effective communication |
| Syncope | The loss of an unstressed vowel |