Learn Italian: La mia stanza è ordinata, la tua no.

In Italian, when a possessive word like tua stands alone to mean "yours" (acting as a pronoun), it usually still needs its definite article. Here, la tua replaces the full phrase la tua stanza.

How do I know whether to use "il tuo" or "la tua" for "yours" here?

The possessive pronoun must match the gender and number of the noun it replaces. Since la tua refers back to la stanza (a feminine singular word), you must use the feminine singular form la tua.

Why does ordinata end in -a?

Ordinata means "tidy", and as an adjective, it must agree with the noun it describes. Because stanza is feminine singular, the base word ordinato changes its ending to -a.

Why does the sentence end with just no instead of non è?

When contrasting a positive statement with a negative one, Italian often just uses no to mean "is not" or "does not". Saying la tua no is a natural, conversational way to say "yours is not" without repeating the verb.