"The boy does not eat the green tomato."
Translation:Il ragazzo non mangia il pomodoro verde.
Some adjectives have four forms like rosso ( red ) nero ( black ), while others have only two like verde (green) triste ( sad ). I hope the following site will help http://italian.about.com/library/fare/blfare128a.htm ....and of course there are a few sneaky ones like rosa ( pink ) that have only one.
Ok, I think I see now. There's no rule though? I just have to memorize what adjectives have multiple forms?
Actually most adjectives have multiple forms. The ones that don't are the exceptions.
If the adjective end in the letter o (ie. rosso), it will usually have four forms, one each for: masculine singular, feminine singular, masculine plural, feminine plural (in order: rosso, rossa, rossi, rosse)
If the adjective end in the letter e (ie. verde), it only has two forms: singular and plural (verde, verdi). These adjectives are called gender invariant (because they don't change with the gender of the noun)
Then there are invariant adjectives (adjective that don't change to match the noun at all). You just have to memorize these... Examples include blu, marrone, rosa.
Overall though the vast majority of adjectives you will come across will change to match the noun (in number at least, and often in gender as well)