Innersprings are metal coils that are used in the construction of mattresses. However, there are several synonyms for the word 'innersprings' that can be used in place of the word if desired. These synonyms include: innerspring system, coil system, spring system, spring unit, bed base, and inner coil system. Each of these synonyms describes the same type of product, but they can be used interchangeably depending on the context and the writer's personal preference. Regardless of which term is used, innersprings remain a popular option for creating a supportive and comfortable sleeping surface.