Proto Norse language

Phonology

Proto-Norse phonology probably did not differ substantially from that of Proto-Germanic. Although the phonetic realisation of several phonemes had probably changed over time (as with any language), the overall system of phonemes and their distribution remained largely unchanged.

Consonants

1. /n/ assimilated to a following velar consonant. It was [ŋ] before a plain velar, and probably [ŋʷ] before a labial-velar consonant.
2. Unlike its Proto-Germanic ancestor /x/, the phoneme /h/ was probably no longer a fricative. It eventually disappeared except word-initially.
3. [β], [ð] and [ɣ] were allophones of /b/, /d/ and /ɡ/, and occurred in most word-medial positions. Plosives appeared when the consonants were lengthened (geminated), and also after a nasal consonant. Word-finally, [b], [d] and [ɡ] were devoiced and merged with /p/, /t/, /k/.
4. The exact realisation of the phoneme /z/, traditionally written as ʀ in transcriptions of runic Norse, is unclear. While it was a simple alveolar sibilant in Proto-Germanic (as in Gothic), it eventually underwent rhotacization and merged with /r/ towards the end of the runic period. It may have been pronounced as [ʒ] or [ʐ], tending towards a trill in the later period. The sound was still written with its own letter in runic Old East Norse around the end of the millennium.

Vowels

The system of vowels differed somewhat more from that of Proto-Germanic than the consonants. Earlier /ɛː/ had been lowered to /ɑː/, and unstressed /ai/ and /au/ had developed into /eː/ and /ɔː/. Shortening of word-final vowels had eliminated the Proto-Germanic overlong vowels.

1. /o/ had developed from /u/ through a-mutation. It also occurred word-finally as a result of the shortening of Proto-Germanic /ɔː/.
2. The long nasal vowels /ɑ̃ː/, /ĩː/ and /ũː/ occurred only before /h/. Their presence was noted in the 12th century First Grammatical Treatise, and they survive in modern Elfdalian.
3. All other nasal vowels occurred only word-finally, although it is unclear whether they had retained their nasality in Proto-Norse or had already merged with the oral vowels. The vowels /o/ and /ɔ̃/ were contrastive, however, as the former eventually developed into /u/ (triggering u-mutation) while the latter was lowered to /ɑ/.
4. The back vowels probably had central or front allophones when /i/ or /j/ followed, as a result of i-mutation:
5. /ɑ/ > [æ], /ɑː/ > [æː]
6. /u/ > [ʉ], /uː/ > [ʉː] (later /y/, /yː/)
7. /ɔː/ > [ɞː] (later [œː] or [øː])
8. /o/ did not originally occur before /i/ or /j/, but it was later introduced by analogy (as can be seen on the Gallehus horns). Its allophone was probably [ɵ], later [ø].
9. Towards the end of the Proto-Norse period, stressed /e/ underwent breaking, becoming a rising diphthong /ja/.
10. Also towards the end of the Proto-Norse period, u-mutation began to take effect, which created rounded allophones of unrounded vowels.

Diphthongs

At least the following diphthongs were present: /æi/, /ɑu/, /eu/, /iu/.

1. /ɑu/ was later rounded to /ɒu/ due to u-mutation.
2. /eu/ eventually underwent breaking to become the triphthong /jɒu/. This was preserved in Old Gutnish, but simplified to a long rising /joː/ or /juː/ in other areas.
3. As /iu/ occurred exclusively in environments with i-mutation, its realisation was probably fronted [iʉ]. This then developed further into [iy], which then became /yː/.

Accent

Old Norse had a stress accent which fell on the first syllable. Several scholars have proposed that Proto-Norse also had a separate pitch accent, which was inherited from Proto-Indo-European and has evolved into the tonal accents of modern Swedish and Norwegian, which in turn have evolved into the stød of modern Danish. Another recently advanced theory is that each Proto-Norse long syllable and every other short syllable received stress, marked by pitch, eventually leading to the development of the Swedish and Norwegian tonal accent distinction. Finally, quite a number of linguists have assumed that even the first phonetic rudiments of the distinction didn't appear until the Old Norse period.

Proto-Germanic to Proto-Norse

The differences between attested Proto-Norse and unattested Proto-Germanic are rather small, though substantial, as several hundred years separate these language stages. Separating Proto-Norse from Northwest Germanic can be said to be a matter of convention, as sufficient evidence from the remaining parts of the area (i.e. Northern Germany, the Netherlands etc.) is lacking in a degree to provide sufficient comparison. Inscriptions found in Scandinavia are considered to be in Proto-Norse. Several scholars argue about this subject matter. Wolfgang von Krause, for one, sees the language of the runic inscriptions of the Proto-Norse period as an immediate precursor to Old Norse, but Elmer Antonsen views them as Northwest Germanic, though his views on Runic Script and related subjects might be considered extreme.

One early difference shared by the West Germanic dialects is the monophthongization of unstressed diphthongs. Unstressed *ai became ē, as in haitē (Kragehul I) from Proto-Germanic *haitai, and likewise unstressed *au became ō. Characteristic is also the Proto-Norse lowering of Proto-Germanic stressed ē to ā; this is demonstrated by the pair Gothic mēna and Old Norse máni (English moon). Proto-Norse differs from the early West Germanic dialects in this respect, as West Germanic ē was lowered to ā regardless of stress; in Old Norse, earlier unstressed ē surfaces as i. Compare for example the weak third-person singular past tense ending -dē, which appears in Old High German as -ta with a low vowel, but in Old Norse as -ði with a high vowel.

When the phoneme /z/, a voiced apical alveolar fricative, represented in runic writing by the *Algiz-rune, changed to /R/ an apical post-alveolar approximant, is debated. Taken into account the general Proto-Norse principle of devoicing of consonants in final position, a retained */z/ would have been devoiced to an *[s], and would be thus realized in runes. There is, however, no trace of this in the Elder Futhark runic inscriptions, ergo it can be safely assumed that the quality of this consonant must have changed before the devoicing, otherwise the phoneme would not have been marked with a rune separate from the rune used for /s/. The quality of this consonant is only determined from conjecture, and the general opinion is that it has to be something between /z/ and /r/, which is the Old Norse reflex of the sound. In Old Swedish, the phonemic distinction between /r/ and /R/ was retained into the 11th century, as exhibited by the numerous rune stones from Sweden from that period.

Proto-Norse to Old Norse

In the period 500–800, two great changes occurred within Proto-Norse. Umlauts appeared, which means that a vowel was influenced by the succeeding vowel or semi-vowel, e.g. Old Norse gestr (guest) came from P-N gastiz (guest). There was another kind of sound change known as vowel breaking in which the vowel changed into a diphthong, e.g. hjarta from *hertō or fjǫrðr from *ferþuz.

Umlauts resulted in the appearance of the new vowels y (e.g. fylla from *fullijaną) and œ (e.g. dœma from *dōmijaną). The umlauts are divided into three categories, A-umlaut, I-umlaut and U-umlaut; the latter was still productive in the Old Norse era. The first, however, appeared very early, and its effect can be seen already around 500 on the Golden Horns of Gallehus. The variation caused by the umlauts was by and in itself no great disruption in the language. It merely introduced new allophones of back vowels if certain vowels were in following syllables. However, the changes brought forth by syncope made the umlaut-vowels a distinctive non-transparent feature of the morphology and phonology, i.e. phonemicizing what were previously allophones.

Due to syncope, the long vowels of unstressed syllables were shortened and many shortened vowels lost. Also, most short unstressed vowels were lost. As in P-N the stress accent lay on the first syllable words as P-N *katilōz became ON katlar (cauldrons), P-N horną was changed into Old Norse horn and P-N gastiz resulted in ON gestr (guest). Some words underwent even more drastic changes, like *habukaz which changed into ON haukr (hawk).