Learn Portuguese (Portugal): As médicas são bonitas.

In Portuguese, words that describe a noun must match its gender (masculine or feminine) and number (singular or plural). Because médicas is feminine and plural, the word for "the" must be As and the adjective must be bonitas.

Why do we use são instead of é for "are" in this sentence?

são is the form of the verb ser (to be) used for "they" (eles or elas). Since we are talking about multiple doctors, we use são. If it was just one female doctor, we would use é (A médica é bonita).

How do you form the plural of a word like médica?

For most Portuguese words that end in a vowel, you simply add an s to the end. So médica becomes médicas, and bonita becomes bonitas.

What if the group of doctors has both men and women in it?

If a group includes even one male, Portuguese defaults to the masculine plural. You would change the entire sentence to Os médicos são bonitos. You only use As médicas when every single doctor in the group is female.