History of the english language

-o- and -u- stems in Old English had only three distinctive endings both for the singular and the plural and that was sufficient for proper communication. -i- stems, on the other hand, illustrate the tendency to dissolution of the former classes of nouns and a certain tendency for regrouping the declensions according to the gender of the noun.
Weak Declension
This class of nouns consists of a rather numerous group of nouns originally having - n-stems; the suffix is well-preserved in declension of nouns in Old English, but disappeared in the nominative case. -n- stem nouns may be of all three genders.
Examples:masculine: wita (wise man), steorra (star), flota (ship, fleet), neuter: cofa (chamber, repositary). feminine: heorte (heart), sunne (sun), hearpe (harp).
Root Stems. This group comprises the nouns that never had a stem suffix.The group was not numerous, but the words belonging to it were characterised by high frequency of use.
The nouns of this class are:all compound nouns containing the morpheme man: wimman (woman), ealdorman (nobleman, leader),and also f ōt (foot), mūs (mouse). The nouns belonging to -r-stems were of masculine and feminine gender, the group is a closed system. Ex. are dohtor (daughter), sweostor (sister)
Less numerous and less significant for the development of the present- day nominal system are the nouns that had other consonants as a stem- forming suffix, -s- stems had had this suffix in older times, in Old English due to rhotacism they changed it into occasional appearance of -r- sound in indirect cases. They are all neuter.
Comparatively new for Old English are several substantivated participles forming a separate group of -nd- stems. They are all masculine and their declension combines the peculiarities of the declension of -a-stems and, to some extent, -r- stems as they all denote persons (they may form their plural form without any ending). Here belong such words as wealdend (ruler), scyppend (creator) etc.