Old High German is an inflected language, and as such its nouns, pronouns, and adjectives must be declined in order to serve a grammatical function.
Often intervening sound changes render the once transparent stem endings opaque, and the name may no longer make much sense synchronically.
And even diachronically; the i-, ja-, and jō-stems lose their overt i’s in all inherited forms except the masculine and neuter nominative-accusative case during the ninth century.
Examples of masculine nouns declined like tag "day": bërg "mountain", wëg "way", geist "spirit", himil "heaven", tiufal "devil", kuning "king".
Notes: Examples of neuter nouns declined like wort: barn "child", sēr "pain", swërt "sword", honag "honey".
[2] Sample nouns of this declension: gëba "gift", ërda "earth", ēra "honor", zala "number", triuwa "fidelity", corunga "temptation", hertida "hardness", miltida "compassion", gi-nāda "favor", lōsunga "deliverance", stunta "time".
Sample nouns like sunta: hella "hell", sibba, sippa "peace", minna "love", krippa "manger".
Sample nouns like kuningin: forasagin "prophetess", friuntin "friend", burdin "burden".
Notes: This class consists of feminine abstract nouns and came about through the falling together of two declensions that were still different in Gothic: compare the Gothic -ei stems (a subclass of the weak declension, formed from adjectives, e.g. diupei "depth", genitive diupeins, from diups "deep") and -eins stems (a subclass of the i-declension, formed from Class I weak verbs, e.g. dáupeins "a dipping", genitive dáupeináis, from dáupjan "to dip").
Examples of other members of this class: scōnī "beauty", suoẓẓī "sweetness", snëllī "quickness", tiufī "depth", menigī, managī "multitude", irstantanī "resurrection", toufī "a dipping", welī "choice", leitī "a leading", riudī "mange".
A large number of nouns belong to this declension, such as fīant "enemy", wīgant "warrior", and many others in -ant.
Formally, these nouns look like regular neuters except that a suffix -ir (from Proto-Germanic -iz-, from Proto-Indo-European -es-) is added to the stem in the plural and triggers umlaut.
This represents a significant innovation in Germanic, although a similar development has taken place in the Baltic and Slavic languages.
The –ēr and –iu endings are also innovations specific to Old High German, based on the third-person personal pronouns.
Other examples of such adjectives are festi "fast", māri "famous", tiuri "dear", biderbi "useful", as well as present participles, such as bëranti "bearing".
Other examples of such adjectives are gëlo "yellow", zëso "right(-handed)", slēo, slē "dull", frao, frō "joyful", rao, rō "raw".