1.perennial a．长期的(perpetual);n．多年生植物(perennial plant)

词根记忆：per+enn(年)+ial--年到头的--长期的

例：perennial problem//The root systems of most flowering perennials always become too crowded.

派生词：perennially( ad.长期地)

2.performance n.性能(the manner in which a mechanism performs)；表演(the action of representing a character in a play)：成绩，绩效(sth. accomplished)

词根记忆：来自perform(v.执行；表演)

例：Such legislation would duplicate initiatives already being made by corporate boards to improve their own performance.

3.perfunctory a．草率的；敷衍的(lacking in care, interest or enthusiasm)

词根记忆：per(表面)+funct(做)+ory--做表面功夫--敷衍的

例：Victorian criticism of works by women writers was perfunctory.

4.perimeter n．周长(the length of the outer edge of a closed geometric shape)

词根记忆：peri(周围)+meter(测量)--周长

例：The perimeter of the rectangular garden is 360 feet.

5.periodic a．周期的，定期的(occurring or recurring at regular intervals)

词根记忆：来自period(n．周期)

例：They still display periodic behavior, continuing to burrow on schedule for several weeks.

派生词：periodically( ad.定期地；周期性地)

同根词：aperiodic(a．不定期的；非周期性的)

6.periodical a．周期的，定期的(periodic)；期刊的(published in，characteristic of, or connected with a periodical);门．期刊(a periodical publication)

例：The total of the expenditure for periodicals and newspapers was 25 percent less than the expenditure for books.

periodically( ad.周期性地)

7.periphery n.外围(the outward bounds of something as distinguished from its internal regions or center)

词根记忆：peri(周围)+pher+y--带到周围--外围

例：Most of the offices and classrooms were in the center of the college campus, and the dormitories were on the periphery.

派生词：peripheral(a．外围的)

8.perishable a．易腐败的(likely to decay or go bad quickly);n．易腐败的东西(stuff subject to decay)

词根记忆：来自perish(v.腐烂)

例：Cooking is usually the final step in preparing food for consumption, whereas irradiation serves to ensure a longer shelf life for perishable foods.

派生词：perishability(n.非持久性：易腐性)

同根词：perisher (n.讨厌的人；死亡之物)

9.permanent a．永久的(lasting)；固定的(stable)

联想记忆：per(贯穿)+man(人类)+ent(…的)--贯穿人类历史--永久的

例：The lssei(第一代移居北美的日本人)formed a permanent, family-based community.

派生词：permanently( ad.永久地，固定地)