Questo and quello: this and that

Questo usually indicates something near the speaker: this. Quello indicates something more distant: that. Distance need not be physical; these words also refer to things being discussed.

Questo, questa, questi and queste agree with the noun. Before a vowel, the singular is often written quest’: quest’amico, quest’amica. The plural keeps questi and queste.

Its forms follow a pattern similar to the definite article:
quel libro → quei libri;
quello studente → quegli studenti;
quell’amico → quegli amici;
quella casa → quelle case;
quell’amica → quelle amiche.

When replacing a noun, use quello, quella, quelli or quelle: Quelli sono miei. Do not use quel or quei here. Do not add a definite article before questo or quello in this use.

Questo agrees in gender and number. Before a noun, quello changes form like the article. Compare quei libri with quelli on its own.