Demonstrative pronouns, like English words “this” and “that,” point at something. They’re often used as adjectives, as in, “this book” or “that tree.” In English, demonstrative pronouns take a different form in the plural:

Singular   Plural

hic, haec, hoc;   hi, hae, haec;

huius, huius, huius;   horum, harum, horum;

huic, huic, huic;   his, his, his;

hunc, hanc, hoc;   hos, has, haec;

hōc, hac, hōc.   his, his, his.

Singular  Plural

ille, illa, illud;   illi, illae, illa;

illius, illius, illius;  illorum, illarum, illorum

illi, illi, illi;   illis, illis, illis;

illum, illam, illud;  illos, illas, illa;

illo, illā, illo   illis, illis, illis.