意大利语语法：Bello e Quello

The adjectives bello (beautiful, handsome, nice, fine) and quello (that) have shortened forms when they precede the nouns they modify. Note that the shortened forms are similar to those of the definite article.

MASCHILE

Singolare

Plurale

bello/quello

begli/quegli

(before s + consonant or z)

bel/quel

bei/quei

(before other consonants)

bell’/quell’

begli/quegli

(before vowels)

FEMMINILE

Singolare

Plurale

bella/quella

belle/quelle

(before all consonants)

bell’/quell’

belle/quelle

(before vowels)

Chi è quel bell’uomo? (Who’s that handsome man?)

Che bei capelli e che begli occhi! (What beautiful hair and eyes!)

Quell’americana è di Boston. (That America woman is from Boston.)

Quelle case sono vecchie. (Those houses are old.)

Bello retains its full form when it follows the noun it modifies or the verb essere.

Un ragazzo bello non è sempre simpatico. (A handsome boy is not always a likable boy.)

Quel ragazzo è bello. (That boy is handsome.

From:https://www.dbfei.com/Article/yidaliyu/201311/7736.html