Vowels
Compared to the other ancient Germanic languages, the morphonological system of Old Icelandic is relatively complex and in many ways irregular. This complexity and irregularity of Old Icelandic stems from the instability of the phonological system and multiple irregular developments, as well as from ambiguity of endings and active processes of analogy. Many of these phenomena took place before Icelandic was established as an individual language, while others affected the language in the course of its internal development.
Some of the most vexing problems related to automated morphological analysis for Old Icelandic are directly related to the morphologically complex phenomena related to the Old Icelandic vowels. These are addressed in the subsections Umlaut and Breaking and Syncope. Another subsection discusses complexities related to consonants in the subsection Consonants.