Learn Italian: Quel cane è grosso e forte. - That dog is big and strong.

The word for that changes depending on the noun it describes, similar to how we choose between the definite articles il, lo, or la. Because cane is a masculine word that takes the article il (il cane), the matching form for that is quel (quel cane). You would use quello before words that use lo, like quello specchio (that mirror).

Could I use grande instead of grosso to mean big?

Yes, you could say Quel cane è grande. However, grosso emphasizes physical bulk, thickness, or heaviness, which is a very common way to describe animals in Italian. Grande can mean large in general, tall, or even great in a non-physical way.

Why does grosso end in -o but forte ends in -e?

Italian adjectives usually fall into two main categories. Grosso belongs to the first category, which ends in -o for masculine singular nouns like cane. Forte belongs to the second category, which contains adjectives that always end in -e in the singular, regardless of whether the noun they describe is masculine or feminine.