The best translation for the underlined word "despedirse" in the sentence "Es triste despedirse de un amigo" is "to say goodbye."
Here's why:
1. "Despedirse" is a reflexive verb in Spanish, which indicates that the subject of the sentence is performing the action on themselves. In this context, "despedirse" means "to say goodbye to oneself" or simply "to say goodbye."
2. When bidding farewell to a friend, you are essentially saying goodbye to them, making "to say goodbye" the most suitable translation in this scenario.
Therefore, the correct translation for "despedirse" in this context is "to say goodbye."
