Errore numero diciannove - Aggettivi e Pronomi Dimostrativi

Another very common mistake is to use demonstrative pronouns (such as that one or those ones) where adjectives should be used, and vice versa. Let me first remind you that a pronoun replaces a noun, whereas and adjective modifies or qualifies a noun. Therefore:

That dog = Quel cane (aggettivo)
That one = Quello (pronome)

A common mistake is to say "quello cane", hence using a pronoun where an adjective should be used

Those dogs = quei cani (aggettivo)
Those one = quelli (pronome)

It would be wrong to say "quelli cani"

It is more straightforward with feminine words, as pronouns and adjectives in that case are the same:

That house = Quella casa (aggettivo)
That one = Quella (pronome)

That island = quell’isola (aggettivo)
That one = quella (pronome)

Those islands = quelle isole (aggettivo)
Those ones = quelle (pronome)