Hello! My name is Alejandra, and the question I'm gonna answer today is: What's the difference between "bueno" and "bien" in Spanish? I'll start by saying that BUENO is an adjective, and BIEN is an adverb. BUENO is equivalent to GOOD, and BIEN is equivalent to WELL. We use BUENO to describe people, things, or situations. ¿Qué tal está tu libro? Muy BUENO. How's your book? Really GOOD. El ejercicio es BUENO para la salud. Exercise is GOOD for your health. We use BIEN to describe an action or a state of being: Irene maneja (o conduce) muy BIEN. Irene drives really well. El proyecto va bien. The project is going well. We use BIEN with the verb ESTAR, never with the verb SER. If we want to say: Emma is well, we don't say: Emma ES BIEN (NO) we say: Emma ESTÁ BIEN (YES) WATCH OUT. 1. BUENO changes to BUEN when it comes before a masculine noun, but it's still an adjective. Sherlock Holmes is a good detective. Sherlock Holmes es un BUEN detective. BUEN is describing Sherlock Holmes as a detective. We remove the O for phonetic reasons. I hope this cleared all your doubts. Remember you can book private sessions with me if you'd like and I'll be happy to be your teacher. Have a nice day!