Learn Spanish (Latin America): Su vestido es moderno, pero no muy cómodo. - Her dress is modern, but not very comfortable.

The word su is versatile and can mean "his," "her," "your" (formal), "its," or "their." You usually know which one it applies to from previous context. If it isn't clear, a Spanish speaker might say el vestido de ella (the dress of hers) to be specific.

Why use es instead of está when talking about clothes being comfortable?

We use es (from the verb ser) because we are describing a fundamental characteristic or the design of the dress itself. It is simply a modern but uncomfortable item. If you were talking about how a person currently feels while wearing it, you would use estar (for example, ella no está cómoda - she is not comfortable).

Why do we use muy here instead of mucho?

Muy translates to "very" and is always used right before adjectives (like cómodo) or adverbs. Mucho translates to "much" or "a lot," and is instead used with nouns (like mucho dinero) or after verbs.

Why do both adjectives end in -o (moderno, cómodo)?