tier
/tɪə(r); tɪr/ n
any of a series of rows (esp of seats) or parts of a structure placed one above the other 一排（尤指座位）; （阶梯式的）一层
a box in the first tier, ie in atheatre （剧院中的）第一排的一个包厢
a wedding-cakewith three tiers/a three-tier wedding-cake 有三层的结婚蛋糕. =>illus at layer 见 layer 插图.