Peripheral
WordNet
adjective
(1) On or near an edge or constituting an outer boundary; the outer area
"Russia's peripheral provinces"
"Peripheral suburbs"
(2) Related to the key issue but not of central importance
"A peripheral interest"
"Energy is far from a peripheral issue in the economy"
"Peripheral issues"
noun
(3) (computer science) electronic equipment connected by cable to the CPU of a computer
"Disk drives and printers are important peripherals"