1.arboreal a．树木的(of or like a tree);栖息在树上的(inhabiting or frequenting trees)

词根记忆：arbor(树)+eal--树木的

例:Their cardiovascular system is not as complicated as that of arbonaral snakes.

2.arch n.拱形：拱门(a typically curved structural member spanning an opening and serving asa support)；a.调皮的，淘气的(playful in a deliberate way）

例:an arch smile

3.archaeological a．考古学的(the scientific study of material remains of past human life and activities)

词根记忆：来自archaeology(n.考古学)

例:They tend to reflect archaeological evidence that has become outdated.

同根词：archaeologist(n.考古学家)

4.archaeology n.考古学(study of ancient civilizations by scientific analysis of physical remains found in the ground)

词根记忆：archae(古)+ology(学科)--考古学

例:A technique called proton-induced x-ray emission, is finding uses in medicine, archaeology and criminology.

派生词:archaeologist(n．考古学家)：archaeological(a．考古学的)

5.archenemy n.天敌：主要敌人(a principal enemy)

词根记忆：arch(主要的)+enemy(敌人)--天敌；主要敌人

例:The wolf remains the archenemy of cattle and sheep.

6.architect n.建筑师，设计师(person who designs buildings)

联想记忆：archi（看作archy统治）+tect(遮蔽)--统治建造人类蔽身之所的人--建筑师

例:A prolific architect worked from the turn of the century until the late 1950's.

派生词:architecture(n.建筑学)；architectural(a.建筑的)

7.ardent a.热心的,热烈的(eager)

词根记忆：ard(热)+ent --热心的，热烈的

例:The president is an ardent supporter of civil affairs.

派生词:ardency(n.热心，热烈)

同根词：arduous(a.费力的)；ardor(n.热心)

8.arid a.干旱的( very dry)；荒芜的(lacking in interest and life)

例:These kinds of plants are normally found in arid regions.

派生词:semiarid(a.半干旱的)

9.aristocracy n.贵族政府，贵族统治( government by people of the highest social class)

词根记忆：aristo(最好的)+cracy(统治)一最好的统治一贵族政府

同根词：aristocratic(a．贵族的，贵族统治的)

10.arithmetic n.算术( calculations using numbers )

例:An arithmetic sequence is a sequence in which each term after the first is equal to the sum of the preceding term and a constant.