Learn Italian: Maria è più magra di Anna. - Maria is thinner than Anna.

In English, we often add "-er" to the end of a short adjective to compare things (like "thin" becoming "thinner"). Italian doesn't do this! Instead, you always put più (more) in front of the adjective. So, "thinner" is literally phrased as "more thin" (più magra).

Why is di used for "than" in this sentence?

When comparing two nouns or names (like Maria and Anna) using più (more) or meno (less), Italian uses the word di to mean "than".

Does magra still have to agree with Maria even though it's part of a comparison?

Yes! Just like in a normal sentence, the adjective must match the gender and number of the person it describes. Since Maria is a single female, we use magra (ending in -a). If we were talking about a man, like Marco, we would say Marco è più magro di Anna.

How would I change this sentence to say Maria is less thin than Anna?

You simply swap out più (more) for meno (less). The rest of the sentence stays exactly the same: Maria è meno magra di Anna.