Differentiating between Demonstrative Pronouns and Demonstrative Adjectives. The four terms this, these, that and those are used to identify and indicate specific objects or people. These four terms can be used either as demonstrative adjectives or demonstrative pronouns. Although these terms are used for both demonstrative adjectives and demonstrative pronouns, there is a big difference between them based on their function and use. The main difference between demonstrative adjectives and demonstrative pronouns is that demonstrative adjectives modify a noun whereas demonstrative pronouns replace a noun.