A convertible couch is a piece of furniture that can be used as both a SOFA and a bed. It is composed of three parts: a DAYBED, a SOFA, and a sofabed. A DAYBED is a type of bed that typically has a back and sides, and can be used as a SOFA during the day. A SOFA is a piece of furniture with a back and arms, designed for seating two or more people. A sofabed is a combination of a SOFA and a bed, which can be converted from one to the other.