1.substrate n.底土层，底土(subsoil)
词根记忆：sub(下面)+strate(层)--下面一层--底土层
例：a substrate of clay粘土层
2.subtle a．细微的(delicate)
例：Coral reefs are sensitive to subtle changes in nutrient input to their waters.
派生词：subtly( ad.敏锐地：精巧地)
3.subtract v.(from)减，减去(to deduct)
词根记忆：sub(下面)+tract(拉)--拉到下面--减去
例：Tom subtracted the smaller number from the larger number.
派生词：subtraction(n．减法)
4.subtraction n．减法：减少(an act, operation, or instance of subtracting)
词根记忆：来自subtract(v.减去，扣掉)
例：subtraction formula 减法公式
同根词：subtract(v.减去，扣掉)
5.succession n．连续(sequence);继位（the right of a person or line to succeed）；【生】自然演替(unidirectional change in the composition of an ecosystem as the available competing organisms and especially the plants respond to and modify the environment)
词根记忆：success(接替)+ion--接替发生--连续
例：in succession连续//plant succession植物的自然演替
同根词：successive(a．连续的)；successor(n.继任者;继承人)
6.sue v.向…起诉，提起诉讼(to seek justice or right from a person, etc., by legal process)
发音记忆：“诉”--起诉
例：In 1979, the parents of a three year old sued in New York for accidental-death damages and won an award of $750,000.
7.sufficiency n．足量，充足（the quality or state of being sufficient）
词根记忆：来自sufficient(a．足够的，充分的)
例：Participation in the workplace and economic self-sufficiency, they, believed, would make women socially useful and therefore deserving of equality with men.
8.sufficient a．足够的(enough to meet the needs)
词根记忆：来自suffice(v.使满足：有能力)
例：Some areas of ocean in the Southern Hemisphere do not contain sufficient nutrients to support large seaweed farms.
派生词：sufficiency(n．足够，充足)；sufficiently( ad.充分地)
9.suffrage n．选举权，投票权(the right of voting)
词根记忆：suf+frage(裹示拥护的喧闹声)--投票权
例：It was stronger than their commitment to the suffrage struggle.
派生词：suffragist(n．妇女政权论者)