Of or pertaining to punishment, to penalties, or to crimes and offenses; pertaining to criminal jurisprudence Enacting or threatening punishment; as, a penal statue; the penal code
subject to punishment by law; "a penal offense" serving as or designed to impose punishment; "penal servitude"; "a penal colony" of or relating to punishment; "penal reform"; "penal code
A penal institution or colony is one where criminals are kept as punishment. imprisoned on an island that has served as a penal colony since Roman times