Þrjótrunn distinguishes four cases, the nominative, the accusative, the
dative, and the genitive, and three genders, the feminine, the masculine,
and the neuter, and two numbers: the singular and the plural.
In disyllabic stems the umlaut phenomena are complicated
since the intermediate vowel intervenes and usually
triggers umlaut itself in some of the forms.
Therefore, the umlaut hints are vague. In general
the second stem vowel umlauts the first vowel in the forms
marked with [+]. [u] also means [+] if the second
stem vowel is not -a-.
If the second stem syllable contains -i- and does not
end in -n or -m, then these forms show i-umlaut.
gen.pl.
ending is only -u
If the ending starts with a vowel, the vowel of the second stem
syllable is dropped and sandhi apply.
The second stem vowel often prevents
umlaut by the ending or triggers it itself.
Latin stems in -i with a heavy first syllable, like 'fília',
were often adjusted in the singular. The regular sound changes
would have yielded the ending -i in all four singular cases,
but by similarity with the other 1st declension nouns,
the -i was dropped in nom. and acc.
The gen.pl. of disyllabic words is regularised; for most
words, the ending had dropped, taking with them part of the
stem, yielding totally irregularly modified stems. This was
adjusted for most words, reconstructing -u ending from other
words belonging to this declension.
This sometimes ends in -u (depending on whether
the stem was heavy or light in ancient times).
Participles never end in -u here.
If the ending starts with a vowel, the vowel of the second stem
syllable is dropped and sandhi apply.
The second stem vowel often prevents
umlaut by the ending or triggers it itself.
The dat.pl. was often adjusted to be more regular. Many
disyllabic words would be irregular here.
jökur < *ekwus, and other words that originally had an
-e- stem, were often adjusted in dat.sg, acc.dat.pl, when
sound changes produced ö- instead of jö- in the stem. In
older texts, forms like 'ökkva' can be found.
ending is only -r and dropped after -ll and -rr,
and fuses with -n to yield -nn
If the ending starts with a vowel, the vowel of the second stem
syllable is dropped and sandhi apply.
The second stem vowel often prevents
umlaut by the ending or triggers it itself.
If the nom. and acc. of sg. and pl. happened to be
homophonous, such words were altered to use the dat.pl.
umlaut for nom. and acc.pl., too, probably to retain
a distinction of number.
When the dat.pl. does not umlaut, then nom.acc.pl end in -a,
probably due to a distinctive emphasis on the ending in earlier
times, introduced in order to distinguish singular from plural
forms. When umlaut made the number obvious, this stress was
not used.
Many original 4th declension (u) nouns changed their declension
class to become 2nd declension nouns.
the second stem syllable in -i- or -u- may also cause
umlaut and breaking in some forms
dat.pl.
stems in -r drop the -r from the stem and the i-
from the ending.
acc.sg.
Some words with (originally) heavy second syllable often
retain an ending -i, e.g., all present participles.
nom.acc.pl.
Stems in -r drop this r before the -ir ending.
If the ending starts with a vowel, the vowel of the second stem
syllable is dropped and sandhi apply.
The second stem vowel often prevents
umlaut by the ending or triggers it itself.
The nom.sg. has lost its original Latin ending (would be -ir) in
most nouns, probably by analogy with (many) irregular nom.sg. forms
that lack the -ir ending and to avoid homophony with nom.pl.
The i declension has vanished but for some irregular nouns.
Both i and mixed declension nouns were reinterpreted as -j
stems.
The neuter declension has collapsed into masc/fem declension,
probably since it had no endings in the plural. Even the rule
that nom=acc was sacrificed to analogy, so that there are now
adjectives that show no gender distinction at all.
Many original 4th declension (u) nouns changed their declension
class to become 3rd declension nouns, using the paradign
of tempvs and corpvs.[1]
This is the original Latin u-declension. Only few nouns
are still in this class. Especially neuter nouns have
often been reassigned to other classes, often the 3rd
declension, sometimes the 2rd declension. Notably plant
and trees are still in this declension. Sometimes even
2nd declension plants were made 4th declension nouns
to make them feminine more easily (e.g. 'þágur' <
fāgvs 'beech'), and also other feminine
2nd declension nouns were moved here.
Some of the words listed above were irregular in
Latin already. Some have undergone such radical
changes (usually frequent, monosyllabic words) that
they are beyond recognition now. Some are original
4th (u) and 5th (e) declension words.
Many original 4th or 5th declension nouns have changed
their declension class today.
The article derives from L. 'ipse'. nom.acc.sg neuter were
obviously borrowed from other words that ended in -ud like 'illud', 'istud',
and 'aliud'. Some of the forms probably
had an unusual stress pattern, or at least, emphasis was
posed on the ending for distinction. This explains why the
article forms retain many more endings than the nouns, although
the original Latin endings are quite similar.
