§ 178. There were two demonstrative pronouns in OE: the prototype of NE that, which distinguished three genders in the sg and had one form for all the genders in the pl. (see Table 6) and the prototype of this with the same subdivisions: pes Masc, pēos Fem., pis Neut. and pās pl. They were declined like adjectives according to a five-case system: Nom., Gen., Dat., Acc, and Instr. (the latter having a special form only in the Masc. and Neut. sg).
Table 6
Declension of sē, sēo, pæt
Case
Singular
Plural
M
N
F
All genders
Nom.
sē, se
pæt
sēo
pā
Gen.
pæs
pæs
pǣre
pāra, pǣra
Dat.
pǣm, pām
pǣm, pām
pǣre
pām, pǣm
Acc.
pone
pæt
pā
pā
Instr.
pӯ, pon
pӯ, pon
pǣre
pǣm, pām
As seen from the table, the paradigm of the demonstrative pronoun sē contained many homonymous forms. Some case endings resembled those of personal pronouns, e.g. -m — Dat. Masc. and Neut. sg and Dat. pl; the element -r- in the Dat. and Gen. sg Fem. and in the Gen. pl. These case endings, which do not occur in the noun paradigms, are often referred to as "pronominal" endings (-m, -r-, -t).
§ 179. Demonstrative pronouns are of special importance for a student of OE for they were frequently used as noun determiners and through agreement with the noun, indicated its number, gender and case. The forms of the pronouns may help to define the forms of the nouns in ambiguous instances, e. g. in the phrases on pǣm lande, tō pære heorde ‘on that land, to that herd’ the forms of the pronouns help to differentiate gender: pǣm is Neut. or Masc. pǣre is Fem.; both nouns are in the Dat. sg and happen to have identical endings: -e. In the following sentences the forms pǣt and pā help to distinguish between numbers:
Uton ... ʒesēon pǣt word (sg) ‘let us see that event’
Maniʒe cōmen to bycʒenne pā ping (pl) ‘many came to buy those things’
(The nouns are Neut. a-stems with homonymous sg and pl forms.)