悲哀: grieved, sorrowful...
应用: to put to use, to apply, practical, applied (science, linguistics etc), application, practical use, (computing) app...
黄昏: dusk, evening, nightfall...
首脑: head (of state), summit (meeting), leader...
纯朴: simple and honest, unsophisticated, guileless...
划时代: epoch-marking...
关键: crucial point, crux, key, crucial, pivotal...
思考: to reflect on, to ponder over...
皮革: leather...
眼界: ken, scope...
