Old English masculine a-stem noun
The nominative/accusative plural form fiscas is the source of plural -s in Modern English, while the genitive singular -es form is the source of the Modern English -'s possessive.
Over one-third of OE nouns were masculine a-stems, while a quarter were feminine o-stems, a quarter were neuter a-stems and 10 per cent were masculine consonant stems. Added to this were some other, minor, declensions, such as mutated plurals (fot, fet).
Old English masculine n-stem noun
It is striking that there is no longer any differentiation in the singular outside nominative, and, while the nominative and accusative plural are opposed to the genitive and dative plural, the nominative and accusative plural are also exactly the same as the accusative, genitive, and dative singular.
While the u-declension originally comprised masculines, feminines and neuters, almost all the neuters and a large number of the masculines changed declensions. The majority of the u-stems are still masculines, however. The chart below features one masculine (magu'man') and one feminine (duru 'door') u-stem noun:
Old English masculine and feminine u-stem noun
The following overview of the set of OE nominal endings illustrates clear cases of syncretism (falling together) of case endings: the masculine and neuter vocalic stem endings in the singular are identical, as are the genitive and dative plural; in fact, all dative plural forms are the same in all stem types (vocalic as well as consonantal), and the tendency is for all genitive plural forms of vocalic stems to be the same. Greater harmony is found in the consonantal stems, in which all genitive and dative singular forms are the same across all genders, while there is no longer any differentiation according to gender in the plural. (NB: elements in parentheses may or may not occur.)
The OE adjective is especially interesting for a variety of reasons. First, there are two sets of forms, termed 'strong' and 'weak': the strong endings are used when the adjective is not accompanied by a marker of definiteness - in this case an article or a demonstrative or possessive pronoun; the weak endings occur when the adjective is preceded by a determiner. Thus:
Gōd mann'(a) good man' vs. Sē gōda mann'the good man'
Second, the cases of the adjective preserve a greater degree of formal differentiation than do the cases of the noun; this is especially true of the strong adjective, in both numbers. In addition, the adjective preserves five distinct cases (i.e., preserving a separate instrumental, something that is no longer obvious in the noun). In the weak adjective, on the other hand, and especially in the plural, syncretism is the rule. There are striking parallels if we compare the weak declension of the adjective with the consonantal declension of the noun above. The full set of adjectival forms, here with the example gōd 'good' is as follows:
Special points to notice are:
(1) the loss of a distinction among the three genders in the nominative singular;
(2) the realization of most forms of the weak singular adjective as gōd-an
(3) the stabilization of one form each in the genitive and dative plural for all genders; and
(4) the complete lack of gender distinction among weak adjectives in the plural.