1.ideographic a．表意文字（符号）的(of or relating to ideogram)

词根记忆：ideo(=idea思想，意义)+graph(写)+ic--把意义记录下来的一表意文字的

例：Chinese consists of tens of thousands of ideographic characters.

2.ideology n.思想体系，意识形态(a set of doctrines or beliefs that form the basis of a political, economic, or other system)

词根记忆：ideo(思想)+logy--思想体系

派生词：ideological(a．思想体系的)

3.idiosyncrasy n．癖好，特性（eccentricity）

词根记忆：idio(个人的，独特的)+syn(共同)+crasy(混合)--混合了个人特性的行为--癖好

例：idiosyncrasies of behavior行为特性

派生词：idiosyncratic（a．特殊的，异质的）

同根词：idiom(n．习语)：idiopathy (n．特发病)

4.idle a．闲置的(not turned to normal use)；无用的(vain)；懒散的(lazy)

例：In this country, growers of certain crops were paid to leave a portion of their land idle.//What you have said is an idle boast.

派生词：idleness(n．闲散，懒惰)

5.ignite v.点燃(to kindle)；着火(to catch fire)

词根记忆：ign(点燃)+ite--点燃，着火

例：Forest fires were ignited by a meteorite impact.

派生词：ignition(n．点火，着火)

6.illegal a．违法的，非法的(unlawful，illicit)

词根记忆：iI（不）+legal(合法的)--不合法的--违法的

例：illegal drugs违禁药物

派生词：illegally( ad.非法地，违法地)

7.illicit a．违法的，不正当的（unlawful）

词根记忆：iI（不）+licit(合法的)--不合法的--违法的

例：illicit trade非法贸易

8.illiterate n.文盲(having little or no education; ignorant)

词根记忆：il（不）+literate(识字的)--不识字的--文盲

例：People between 18 and 24 are more likely to be technologically il1ite,ate than somewhat older adults.

派生词：illiteracy(n.文盲;无学识)

9.illuminate v.照明(to light)；说明(to make clear)

词根记忆：il（加强）+lumin（明亮）+ate--照明

例：Could you please illuminate your theory worth a little more explanation?

同根词：luminous(a.发光的：明亮的)