Peripheral

1. noun

   (computer science) electronic equipment connected by cable to the CPU of a computer

   “disk drives and printers are important peripherals”

   Similar: computer peripheral, peripheral device

2. adjective

   on or near an edge or constituting an outer boundary; the outer area

   “Russia's peripheral provinces”

3. adjective

   related to the key issue but not of central importance

   “a peripheral interest”