Learn Italian: La tua stanza è grande, ma la mia casa è piccola.

In Italian, possessive adjectives like mio (my) and tuo (your) almost always need a definite article (like il or la) in front of them. So instead of just saying "my house", you literally say "the my house" (la mia casa).

Why is it tua and mia instead of tuo and mio?

Possessive adjectives must match the gender and number of the thing being owned, not the person who owns it! Both stanza (room) and casa (house) are feminine singular words. Therefore, we use the feminine singular forms la tua and la mia.

Why does piccola end in -a but grande ends in -e, if they both describe feminine nouns?

Regular adjectives like piccolo (small) change their ending to match the noun exactly (-o for masculine, -a for feminine). Since casa is feminine, it becomes piccola. However, grande (big) belongs to a group of adjectives that naturally end in -e in the singular. These adjectives are used for both masculine and feminine words, so it stays grande for the feminine word stanza.