Kind of, sort of ... replaced.
I'm working on the inflection, and of the indefinite forms only the dative plural is missing.
| a-stem m. | | a-stem n. | | ō-stem f. | |
| nom | arm | armar | bein | bein | leið | leiðar |
| acc | arm | armar | bein | bein | leið | leiðar |
| gen | arm(a)s | arma(s) | bein(a)s | beina(s) | leið/-ar/-(a)s | leiða(s) |
| dat | armi | ? | beini | ? | leiði | ? |
The strong cases (nominative, accusative) seem to have merged, while the weak cases (genitive, dative) still seem to have some difference.
The -um form exists in a few words and phrases, but doesn't seem to exist elsewhere, not even in compounds (either plural is not used or it might be replaced with genitive).
The masculine and feminine singular pronouns can also take the genitive form in place of the dative: hanar, henar; although pronouns are different from content words and more likely to follow separate patterns, so it's not quite as valid.
I've tried compiling compounds to make a complete set, but it's difficult finding words with all the forms:
nom.
arm-boga — arm bow (elbow)
gen. sg.
arm-s-lengð — arm's length (the length of an arm)
gen. pl.
arm-a-mót — arms' meeting (a hug, embrace)
dat.
arm-i-stark — arm strong (
?) (
having great arm strength)
nom.
barn-lékar — child doctor (a doctor who is a child)
gen. sg.
barn-s-lékar — child's doctor (
?) (
a private doctor who treats children)
gen. pl.
barn-a-lékar — children's doctor (a general doctor who treats children)
dat.
barn-i-lékar — child doctor (
?) (
a doctor set aside for treating children)
The dative plural might not even exist :/ Aside from a few relics, it doesn't seem to appear anywhere — or at least not anything that in form looks like dative.
I'm looking to see whether it would be possible to use the genitive singular -ar or plural -a as a dative plural ending. Even though -um exists in a few places, and I understand it just fine, it simply doesn't feel right — it's not used in my language. Dative plural might not exist in compounds, and independently it's mostly for poetic or nonambigous use, it's not something that is required in common speech.
