词根：sid(sed, sit), sess(sid) = to sit 坐
词根sid来源于拉丁语的不定式词干 sidere,词根sess来自动名词词干，都意为to sit（坐）或to settle（安定）。sid为元音弱化后形成的词根。sid,sess属于一对同源异形根，反义词根有来自拉丁语的st,stat,stit,sist等。
同源词：
1. assiduous [一直坐着的as<ad(=to,intensive)+sid(=sit)]
adj.“constant or unwearied in application; diligent 刻苦的；勤奋的：He is assiduous in his study 他学习勤奋。
assiduity [as-; sid;-u-；-ity n.]n.刻苦；勤奋
2. preside [before前；sid= to sit 坐；-e- “to sit before others 坐在其他人前面”] v. sit in authority; act as chairman 主持；作会议主席：
to preside at a meeting 主持会议
presider n.（会议的）主席；主持者
presidium n．主席团；常务委员会
3. president v.主持，当权；-ent n．= person 人 →]
n.person chosen to preside over a nation. university or any other organization 总统；大学校长：会长：社长等
presidency n. 总统等的职位或任期
presidential adj. 总统（或校长等）的
4. reside [re-= back,down 回，下；sid = to sit or settle 坐，安放：-e → "to sit backward, to settle down 靠背安坐，安顿下来” →]
v. make one's home at a place 安家，居住：to reside in the city 在城市居住
resident n. 居民
residence n. 居住；住宅
5. subside [sub- = under,down下；sid= to sit or settle 坐，停留：-e →“to settle down 停在下面，停息”→]
v. ①sink down 下沉；沉降：The building subsides gradually. 这座房子逐渐下沉。
②fall into a state of quiet 平息：The wind has subsided 风停了。
subsidence n.下降；沉降；平息
6. dissident [dis-= apart 分开；sid= to sit 坐；-ent n. = person 人世间→ "person who sits apart from others 与别人分开坐的人”→]
n. person openly disagreeing with an opinion; dissenter 持异议者；反对者：political dissidents 持不同政见者
dissidence [dis-; sid; -ence n.] n. 异议；不一致
7. insidious [in- = in 内；sid= to sit 坐；-i-; -ous adj. = like 像……的_→ "like sitting in a hidden place，like setting an ambush 像坐在暗处的，像打埋伏的”→]
adj. ① intended to entrap 伺机为害的：insidious diseases 暗疾
②deceptive; treacherous 暗中为害的；阴险的：an insidious tempter 阴险的诱惑者
insidiousness n. 阴险；狡诈
8. session [sess= to sit 坐；-ion n. = the act or state 表行为或状态 →]
n. ① act of sitting 坐；就座
②sitting or time of sitting, as of a court or public body 开会；开庭；会期；开庭期：plenary session 全体会议
sessional adj. 开会的；开庭的
9. possess [pos(来自potis) = able 能……的；sess= to sit 坐→ "to be able to sit in a place 能坐在一个位置上”→]
v. ① inhabit or occupy 居住于；占据
② have or hold as property own 具有；占有：He possessed landed property 他拥有地产。
③ maintain or control 保持；控制：She was possessed by the desire to be rich 她被发财的欲望所支配。
possessor [possess; -or n.] n.占有人；所有人
possession [possess;-ion n.] n.占有；占有物；财产；领地
possessive [possess; -ive adj.] adj. 占有的 n.[语法]所有格
10. assess [as-(ad-) = to,at在；sess= to sit坐→“(judges in a court) to sit at or sit by（法官等在法庭）就座”→ "to judge or estimate 作判断，估计”→]
v. ①fix the value or profits of 对……进行估价：His property is assessed at one million dollars 他的财产估价为100万元。
② decide the amount of(a tax)征收（税款）：to assess a tax of ten pounds 征税10镑
assessment [assess; -ment n.] n.估价；评价
assessor [assess; -or n.] n. 估价财产的人；确定税款的人
assessable [assess; -able a.] adj.可估价的；可征税的
11. sedate [sed=sid坐+ate……的→坐着的,文静的]
adj.文静的
12. consider [con全部+sid坐+er→坐在一起→考虑到]
v.考虑,细想;体谅,顾及;认为,把…看作
13. supersede [从上往下坐下 super(=over)+ sed(=sit)]
vt. 代替；取代
supersession n.取代
Model AE-400x supersedes Model AE-200.模型AE-400X取代AE-200。
14. obsession [妨碍地坐着ob(=in the way)+sess(=sit)]
n.着迷；迷住
obsess v.妄想、固有观念等）萦绕心头，不停地困扰
obsessive adj. 使人着迷的
Eating is my hobby. Shopping is my obsession! 吃东西是我的兴趣，购物让我着迷！
15. sedan
n.箱式小客车（可容纳4人以上）；（17 - 18世纪的）轿子
sedan chair 轿子
16. sedimentary
adj.沉渣的，沉淀物的；由沉淀物生成的
sedimentary rocks 沉积岩（如粘板岩、石灰岩等）
17. sedulous
adj.坚忍不拔的；勤勉的，刻苦的；小心周到的
pay him sedulous attention 密切地关注他
18. saddle
n.马鞍； （自行车或摩托车的）车座； 鞍形架，鞍状物； （动物的）脊肉
vt.& vi.给（马）装鞍
vt.使承担
19. possess
v. 持有，拥有；控制；（恶魔、邪念等）缠住，迷住（某人） *pos (=powerful,able)
possess a large fortune 拥有大量财产
be possessed with/by devils 着魔的
be possessed with the idea that someone is persecuting him 着魔地认为有人在迫害他
be possessed by envy 内心充满嫉妒
20. possession
n. 所有；（pl.）所有物；财产 *pos(=powerful,able)
illegal possession of arms 非法持有武器
a man of great possessions 富翁
21. possessive
adj.所有的；所有权的；[语]所有格的；占有欲强的
possessive manner 极具占有欲的态度
possessive adjective/case/pronoun 所有格形容词/所有格/所有格代词
词根：vert, vers = to turn 转, 转向, 转移
词根vert来源于拉丁动词 vertere/versus 转动，词根vers为此词的反复形式 versare 的词干部分，也是动名词 versum 的词干部分，可用来构成动词、名词或形容词。这族同根词数量较大；可理解为：词根 -var- 圆 / 转的变体；词根 -vert- 也可以理解为是根据辅音的交替规律由 -vers- 变来的，属于单辅音交替规律，如：versatile 可转性的、conversion 转化 / 变换、avert 掉转、convert 转化；同义词根有verg，rot和来自希腊语的stroph等，以及来自盎格鲁一撒克逊语的tour。
同源词：
1. avert [a-=awary，vert=turn;’to turn away”，’转移”→移开] [眼睛和脸离开某物转移方向a<ab(=away，from) +vert(=turn)]
vt. 避开(灾难等)，避免(危险等)，转移(目光，思想等)
avertible／avertable adj. 可避免的
I usually avert my eyes if I see someone stumble in the street.（如果看见有人在路上绊倒，我大都会向别处看。）
2. evert v. [e- = ex- =out,vert 转，-->转向外面 -->向着外面] 外翻；翻转
3. inadvertent adj. 不注意的；疏忽的 (in- = not;ad- = to )
inadvertences;ency n.不注意；疏忽
4. pervert v. [per = thoroughly ,vert 转，-->把背对着正直的道路] 曲解；误解；误用 n.堕落的人；性变态者
perversion n. 曲解，误解，变态
perverse adj.刚愎的；任性的
5. universe n. 宇宙；全世界；全人类（把万物合成一体）(uni = one)
universal adj. 全世界的；一般的，宇宙的
6. university n.大学；大学的校舍（把几个学院合成一体）
7. subversive adj. [见上，-ive形容词后缀，…的] 颠覆性的
8. divert v. [di-=dis-分开，离，vert转;’由学习或工作中转移开] 娱乐，使消遣;[转离] 转向，使转移
9. diversion n. [见上，-ion名词后缀] 娱乐，消遣，转向，转移
10. adverse adj. [ad-表示to，vers转;’转过来”→反转→相反→敌对] (在位置或方向上)逆的，相反的，(引申为)敌对的
11. adversity n. [见上，advers(e)逆的，-ity名词后缀，表示情况，状态] 逆境，不幸，苦难
12. adversary n. [见上，advers(e)敌对的，-ary表示人] 对手，敌手
13. divorce v. [di-=dis-分开，散，vorc=vers转;’to turn apart”] 离婚，分离，脱离
14. reverse [re-回，反→倒，vers转]
v. 倒转，翻转，回复，反向
reversion [见上，-ion名词后缀] 倒转，翻转，回复，反向
reversible [见上，-ible形容词后缀，可…的] 可倒转的，可逆的
15. introvert [intro-向内，vert转] 使(思想)
n. 内向，内省，使内弯，内向性格的人
irreversible [ir-不，见上] 不可倒转的，不可逆的
introversion [见上，-ion名词后缀] 内向，内省，内弯
16. extrovert n. [extro-=extra-外，vert转，转向] 外向性格的人
17. convert [con-加强意义，vert转→转变]
v. 变换，转变
conversion n. [见上，-ion名词后缀] 变换，转化
18. versatile adj. [vert 转，转向，-ile 形容词后缀，-->转向多方面的 -->多方面有才艺的] 多才多艺的；多方面的
19. controvert [contro-=contra-相反，相对，vert转;’to turn against”，针锋相对]
v. 争论，辩论，论战，反驳
controversy [见上，-y名词后缀] 争论，论战，争吵
controversial [见上，-ial形容词后缀，…的] 争论的，好争论的
20. invert [in-内，vert转;’内转”→翻转]
v. 倒转，使倒转，使反向，倒置，转换
inverse adj. [见上] 相反的，倒转的
inversion n. [见上，-ion名词后缀] 反向，倒转，转换
inversive adj. [见上， -ive 形容词后缀，…的] 反向的，倒转的
21. diverse [di-=dis-离，分开，分数，vers转;’转离原样”，’转为多样的”]
adj. (和…)不一样的，多种多样的，形形色色的
diversify v. [见上，-i-，-fy动词后缀，使…] 使不同，使多样化
diversified adj. [见上，-ed形容词后缀，…的] 多样化的
diversification n. [见上，-fication名词后缀…化] 多样化
22. diversiform adj. [见上，-form有…形状的] 各种形状的，各式各样的
23. diversity n. [见上，-ity名词后缀，表示性质，情况] 多样性，变化，异样
24. retrovert [retro-向后，vert转;’转向后”]
v. 使向后弯曲，使反转，使后倾
retroversion n. [见上，-ion名词后缀] 后转，后倾，倒退，回顾
25. version n. [vers转，-ion名词后缀;’转”→转换→由一种文字转换为另一种文字→转译→转译的文字] 译文，译本，翻译
26. vertigo n. [vert转→旋转，-igo名词后缀，表示疾病，头’旋转”] 头晕，晕眩，晕头转向
27. vertex n. 顶点；[天文]天顶；[解剖]头顶；[数学]顶点（上升物往下转变的那一点）
28. vortex n.漩涡；旋风（回旋的东西）
29. averse adj. 厌恶的；反对的；不愿意的（回避的态度）
30. advertise v.[ad-表示to向，vert转，-ise动词后缀，使…;’使(人的注意力)转向…”→使人注意到…→引起人注意] 登广告，为…做广告，大肆宣扬
31. advertisement n. [见上，-ment名词后缀，表示行为，行为的结果] 广告，登广告
32. anniversary n.[ann年，-i-，连接字母，vers转，-ary名词后缀;’时间转了一年”] 周年纪念日，周年纪念;[-ary形容词后缀，…的] 周年纪念的，周年的
33. subvert v. [sub-下，由下，vert转.翻转;’由下翻转”] 推翻，颠覆
34. subversion n. [见上，vert=vers，-ion名词后缀] 推翻，颠覆
词根：act, ag = to do, to drive （做, 驱使）
词根 ag 来自拉丁动词 agere 的词干部分，意思相当于英语的 to do （做）或to drive（驱使）。act 是个英语核心单词，其实它的前身 act 是ag的同源异形词根，来自agere（过去分词actus） 的动名词形式 actum 的词干部分，基本含义也是to do 或to drive。
同源词：
1. act
n.行为；法案；一幕
v.
同源词：
1. do something 行动：to act at once 立刻行动；2. function 起作用：The brakes wouldn't act. 刹车失录。3.take part in a play or film 扮演:Who is acting Hamlet ? 谁演哈姆雷特？
actor n.男演员；行动者
actress n.女演员
re-act v.重做，再做；重演，再演
overact v.演得过于夸张
2. action
n. 1. process of doing,or deed 行动，活动：Actions speak louder than words. 行动比语言更有说服力。
2. result of doing ,or effect 作用：the action of an acid on metal 酸对金属的作用
3. charge 诉讼：to bring an action against someone 起诉某人
actionable adj.可控诉的
3. active (act = to do 做；-ive adj.= able 会......的)
adj.able to do 活跃的,积极的：Although he is over 70,he is still active. 他虽然年过70，但依然很活跃。
activate v.使活动
activism n.[哲]能动主义；积极，活跃
activist n.活动分子，积极分子
activity n.能动性；活跃；[复]活动
4. actual（act = to do 做；-u-;-al adj.= the act or fact 表行为或事实）
adj.existing in fact;real 实际的；现实的:the actual amount of money 实际金额
actualist n.现实主义者
actuality n.事实，现在情况；现实性
actualize v.实行，使现实化
5. actuate（act = to do 做；-u-;-ate v.=to make or cause 使......）
v. cause to do 驱动，激励：What motives actuated her ? 什么动机驱使她这样做的？
actuation n.驱动，激励；开动
6. exact （ex- = out 出；act = to drive 驱使-->“to drive out;driven out 逼出来（的）”）
v.demand or obtain by force 强求，索取：He exacted obedience from his students. 他强要学生服从他。
adj.correct and without mistake 准确的，精确的：to be exact in conduct 行为一丝不苟
exacting adj.苛求的，严厉的；强索的
exaction adj.强索的；勒索；榨取
exactutude n.精确（性）；严格，严谨
7. react （re- = back 回返；act = to do 做）
v.
同源词：
1. do or act in reply 反应：She was slow to react. 她反应迟钝。
2. do against 反动，反作用：to react against oppression 反抗压迫
reaction n.反应；反作用；反动
reactor n.引起反应的人或物；[原]反应堆
reactive adj.反应的；反动的
8. interact （inter- = between 在......之间；act = to do 做 --> “to do between two things 在两者之间互动”）
v.have an effect on each other 互相作用，互相影响：All things are inter-related and interacted on each other. 一切事物都是互相联系又互相影响的。
interaction n.相互作用；相互
interactant n.[化]反应物
interactive adj.互相作用的；[计]交互的
9. transact（trans- = across or through 穿过；act = to drive 驱使 --> “to drive through 使通过”）
v. carry on;manage 执行，办理：He transacted some business at bank. 他在银行处理了一些事务。
transaction n.办理，处理；交易，业务
transactor n. 办事人，处理者
10. enact
vt.制定法律, 扮演, 颁布 *en(=in)
11. exactitude
n. 正确；精密；严正《-itude 抽象名词后缀》
12. inaction
v.不活动；懒散；怠惰《in- = not》
inactive adj.不活动的；不活泼的；懒惰的
13. agent
n.代理人；代理商；动作者；原动力（做的人）
14. agile
n.动作的敏捷；机敏
15. agitate
v. 震动；煽动
16. agitation
n.摇动；激动的状态；煽动
17. agitator
n.煽动者；游说者
18. agony
n.极大的痛苦；精神上的激动（缠绕心头）
19. cogent
adj.强有力的；使人信服的（劝动另人一起去）《co- = com- = together》
20. cogitate
v.思考；计划；设计
21. cogitable
adj.可思考的；可想象的
22. exigent
adj.急切的；紧急的；所需极多的（驱逐出去）《ex- = out;ig = act = to act》
23. prodigal
adj.浪费的；挥霍的
n.浪费者；浪子《拉丁文 prodigere = to drive forth》
词根词缀：-arian
【来源及含义】Latin: a suffix forming adjectives from nouns ending in -ary; a person who, a thing that; a person who is a part of something, pertaining to one's state or condition; a person who has a connection with or belief in the stated subject; an advocate of something; a native or inhabitant of someplace; someone of a certain age
【同源单词】abecedarian, acararian, acarian, agrarian, alphabetarian, altitudinarian
词根词缀：bas-, baso-, basi-, ba-, bat-
【来源及含义】Greek > Latin: stepping, to step, to go, to walk; a place where someone steps; a pedestal; a foot for stepping; foundation, ground, base
【同源单词】abasia, acrobat, base, base, based, bases
词根词缀：doul-, dulo-, dul-
【来源及含义】Greek: slave, servile, slavish; servitude; serving
【相关描述】A doula supports a woman and her family in achieving the kind of birth that they desire. A doula works in homes, hospitals, and birth centers; and gives, emotional, physical, and informational support. A careprovider, be he/she a midwife, OB/gyn, or family practitioner, will take care of a woman's prenatal care and birth. A doula is supposed to ensure that someone is always available to look after the mother-to-be emotionally. These objectives are facilitated by communication between the laboring woman, her partner, and her clinical care providers.
As a supportive companion (other than a friend or loved one) a doula is professionally trained to provide birth-labor support. She performs no clinical tasks. A doula also refers to lay women who are trained or experienced in providing postpartum care—mother and newborn care, breastfeeding support and advice, cooking, child care, errands, and light cleaning—for the family. To distinguish between the two types of doulas, one may refer to "birth doulas" and "postpartum doulas".
【同源单词】doule, doulios, doulos, dulia, dulocracy, hierodule
词根词缀：-ist
【来源及含义】Greek > Latin: a suffix; one who believes in; one who is engaged in; someone who does something
【同源单词】abiogenist, abolitionist, abortionist, abrakophile, absolutist, absurdist
词根词缀：laud-
【来源及含义】Latin: praise, praising; glorify, glorifying; showing or expressing strong approval or admiration for something or someone
【同源单词】collaud, collaudation, cum laude, illaudable, laud, laudability
词根词缀：logo-, log-, -logia, -logic, -logical, -logism, -logician, -logian, -logue
【来源及含义】Greek: talk, speak; speech; word; a person who speaks in a certain manner; someone who deals with topics or subjects
【相关描述】Words that utilize -ology are in a separate unit. All -ology words can be made into -ologistic forms.
【相关词根词缀】Cross references of word families related directly, or indirectly, to: "talk, speak, speech; words, language; tongue, etc.": cit-; clam-; dic-; fa-; -farious; glosso-; glotto-; lalo-; linguo-; locu-; loqu-; mythico-; -ology; ora-; -phasia; -phemia; phon-; phras-; Quotes: Language,Part 1; Quotes: Language, Part 2; Quotes: Language, Part 3; serm-; tongue; voc-. Related "word, words" units: etym-; legi-; lexico-; locu-; onomato-; -onym; verbo-.
【同源单词】alogia, alogic, analog, archaeogeological, archaeological chemistry, archaeological chronology
词根词缀：mania-, -mania, -maniac, -maniacal, -manic, -manically, -maniacally
【来源及含义】Greek: a specific mental disorder or obsessive preoccupation with something; madness, frenzy; obsession, or abnormal desire for or with something or someone; also, an excessive enthusiasm or fondness for something
【相关词根词缀】 Cross references of word families that are related directly, or indirectly, to: "anger, angry; rage, wrath, fury; rave": fur-, furi-; ira-; lysso-; rab-, rav-.
【同源单词】ablutomania, aboulomania, acromania, acronymania, adipomania, aedoeomania