plain to对 ... 是清楚的plainadj.清楚的；简单的；坦白的；平常的；朴素的；纯的n.平原；广阔的区域adv.完全地；纯粹地plain river networks平原河网plain miller machine平面铣床plain-carbon steel碳素钢plain coloured towel素色毛巾plain capillary tube扁平(形)毛细管plain artificial fur素色人造毛皮Plain Indian Culture大草原印第安人文化plain antenna system简易天线设备Plain-backed Pipitn.纯背鹨plain calliper gauge普通卡规