1.extend v.延展，延長(to spread or stretch forth)

詞根記憶：ex(出)+tend(伸展)--伸出去--延展

例：The installments(分期付款)will extend over a period of exactly 3 years.

派生詞:extension(n.延伸;提供)；extended(a．延長的)

2.extensive a．大量的；多方面的，廣泛的(having wide or considerable extent)

詞根記憶：來自extend(v.延伸；推廣)

例：His extensive experience in other parts of Asia helped him to overcome cuttural barriers.

派生詞:extensively( ad.廣闊地)

同根詞：extent(n.程度;范圍)

3.exterminate v.消除，消滅（to get rid of completely, usually by killing off）

詞根記憶：ex（出）+termin（界限）+ate--超出生存的界限--消除

例：By the 1930's, bounty hunters had exterminated most of the gray wolves in the United States.

4.external a.外面的，表面的(outside)

詞根記憶：ex(外)+ternal一外面的，表面的

例：external environment外部環境

5.extinct a．滅絕的(no longer existing)；（火山等）熄滅的(no longer active)

詞根記憶：ex+tinct(促使)一使…失去--滅絕的

例：Unless tiger hunting decreases, tigers will soon be extinct in the wild.

派生詞:extinction(n.消失，廢止)

同根詞：distinction（n.差別）：instinct(n.本能，天性)；extinguish(v.熄滅，消滅)

6.extinction n．消滅，廢除(the process of eliminating or reducing a conditioned response by not reinforcing it)

詞根記憶：來自extinct(v.使熄滅)

例：The extinction of the salmon populations that spawn in polluted streams is accelerated.

同根詞：extinctive(a.使消滅的)

7.extinguish v.消滅(to bring to an end)；費息滅(to cause to cease burning)

聯想記憶：ex（出去）+ting( =sting刺)+uish--去掉刺--熄滅

例：Arabs and Bulgarians at times threatened to take Constantinople and extinguish the empire altogether.//Most indMduals have no formal training in how to extinguish fires.