Hola Hankai. "Compañero" is used in relationships: Compañero de piso / Compañero de viaje / Compañero de trabajo / ... "Socio" is used when someone is a partenership in a Company, Club or Organization: Socio de una empresa / Socio del club de natación / Socio de una Organización No Gubernamental (ONG ~ English: NGO) Sometimes, in a colloquial way you can call a friend as "socio" instead "compañero" Saludos. Antonio

Hola...... Compañero. When you use " compañero", in this word is including a friend relationship. You are friend of this person. Socio. When you use " Socio " in this word is not included a friend relationship, it isnot necessary to be friend of your Socio. Sometimes the " SOCIOS " are friends. And sometimes the " socios " are not friends. So you can say " MI compañero de clase " he is my friend and we have many things in common. If you say " MI socio in class " you work with him but he is not your friend, and you can have a good relationship or bad relationship with him. At last. You can have " MI vecino es mi compañero y mi socio " O tengo un socio que no es mi compañero. Thanks bye