tri·ens \ˈtrīˌenz, ˈtrēˌān(t)s\noun (pluraltrien·tes \trīˈen.ˌtēz, trēˈen.ˌtās\) Etymology: Latin, third part, triens; akin to Latin tres three — more at three 1.: a bronze coin of ancient Rome equal to 1/3 as 2.: an ancient Byzantine gold coin equal to 1/3 solidus; also: any of several similar ancient coins (as of Spain)