1.observatory n．天文臺(tái)(a building ,a place, or an institution designed and equipped for making observations of astronomical, meteorological, or other natural phenomena)

詞根記憶：來(lái)自observe(v.觀察)

例：Astronomers at the Palomar Observatory have discovered a distant supernova explosion.

2.obsess v.（使）困擾，（使）著迷( to haunt or excessively preoccupy the mind of)

詞根記憶：ob+sess(=sit坐)--坐著不走--（使）困擾，（使）著迷

例：The fear of death obsessed her throughout her old age.

派生詞：obsession(n.迷住：縈繞)

3.obsolescence n．荒廢；過(guò)時(shí)( the condition of being nearly obsolete)

詞根記憶：來(lái)自obsolete(a.廢棄的)

例：technical obsolescence技術(shù)過(guò)時(shí)

4.obstacle n.障礙(something that impedes progress or achievement)

詞根記憶：ob（反）+st(=stand站)+acle（東西）--反著站的東西--障礙

例：In the speaking contest, Randolph faced formidable obstacles.

5.occupation n．工作，職業(yè)(a job; employment);占領(lǐng)(the act or process of taking possession of a place or area)

詞根記憶：來(lái)自occupy(v.占領(lǐng)；使用)

例：There is no occupation for which the risk of developing an animal- induced allergy is higher than 30 percent.

派生詞：occupational(a．職業(yè)的；占領(lǐng)的)

同根詞：preoccupation(n．全神貫注，入神)

6.occupational a．職業(yè)的（of the activit3t in which one engages）；占領(lǐng)的(taking possession of a place or area)

詞根記憶：來(lái)自occupation（n．職業(yè)：占領(lǐng)）

例：Unlike men of science; women of science have had to work against the grain of occupational stereotyping to enter a "man's world".

同根詞：preoccupation(n．全神貫注；當(dāng)務(wù)之急)

7.occurrence n.發(fā)生(the action or instance of occurring)；事件(sth. that occurs)

詞根記憶：oc(加強(qiáng))+curr(發(fā)生)+ence--發(fā)生

例:It provides an explanation for the occurrence of a situation described in the first paragraph.

同根詞：concur(v.同時(shí)發(fā)生)

8.odd a．奇怪的(peculiar)；奇數(shù)的(impar);n.[pl.]可能性(possibility)；不平等(imparity)

聯(lián)想記憶：奇奇(odd)相加(add)為偶

例：I avoided the odd person who was talking to himself.//The odds are 10 t0 1 against your winning.//against odds盡管有極大的困難//at odds爭(zhēng)執(zhí)，不一致

派生詞：oddity(n.奇特的人或物：古怪的性質(zhì))

9.odometer n.（汽車）里程表（an instrument for measuring the distance traveled as by a vehicle）

詞根記憶：odo(旅行)+meter(測(cè)量)--測(cè)量旅行的東西--里程表

例：I couldn't determine how far l'd driven because my car's odometer is broken.