说明文是对事情的发生、发展、结果、特征、性质、状态、功能等进行解释、介绍、阐述的一种文体.这类文章的目的和性质是客观地介绍、解释事物,使读者获得知识和信息,并不需要发表主张、做出证明.一般说来,知识简介,商品介绍,旅游指南,科技读物,工作总结,实验报告,教材辅导等均属说明文之列.

　　写说明文,可以按时间、空间、结构、逻辑顺序来写,也可以采取举例、比较、对比、分类、分析、说明、叙述等方法.

　　1.比较对照

　　比较对照有两种,一是逐点比较,二是整块比较,即AB交错或先A后B：

　　1）逐点比较：多数人认为这种AB交错的方式可以避免行文的单调沉闷,对比的效果更鲜明突出.如：

　　Therearebasicdifferencesbetweenlargeandsmallenterprises.Inasmallenterprise,youoperatedmainlythroughpersonalcontacts.Inalargeenterprise,youhaveestablished“policies”,“channels”oforganization,andfairlystrictprocedure.Inthesmallenterpriseyouhaveimmediateeffectivenessinaverysmallarea.Youcanseetheeffectofyourworkandofyourdecisionsground.Inthelargeorganizationyouarenormallytaughtonethingthoroughly.InthesmallonethedangerisofbecomingaJack-of-all-trades-but-master-of-none.Inthelargeitisofbecomingthemanwhoknowsmoreandmoreaboutlessandless.

　　2)整块比较

　　Itiseasytobeawinner.Awinnercanshowhisjoypublicly.Hecanlaughandsinganddanceandcelebratehisvictory.Peoplelovetobewithwinners.Winnersareneverlonely.Unlikewinners,losersarethelonelyonesoftheworld.Itisdifficulttofacedefeatwithdignity.Loserscannotshowtheirdisappointmentpublicly.Theycannotcryorgrieveabouttheirdefeat.Theymaysufferprivately,buttheymustbecomposedinpublic.Theyhavenothingtocelebrateandnoonetosharetheirsadness.

　　2.分类

　　分类是人类认识客观世界的重要手段之一,也是描写事物、解释观点最有效的方式之一.通过将一事物分类,可使复杂事物变得清晰明了,便于作者阐述自己的观点.

　　分类段落的各类排列要条理,可采用从主要到次要,从次要到主要,从多到少或从少到多等方式排列,亦可平行排列.如：

　　1）Asfaraspoliticalviewsareconcerned,peoplefallintothreecategories.Firstaretheconservativepeople.Conservativesareopposedtosuddenorgreatchanges.Secondaretheliberalpeople.Thesepeopleareinfavorofprogressandreform.Buttheiropinionsoftenseemtoidealistic.Thethirdtypeisthemoderatepeople.Themoderateskeepeverythingwithinreasonablelimits.Theyaremorepracticalinthishardworld.Inmyopinion,mostpeopleseemtobelongtothisgroup.

　　本段采用平行排列的方式,按人的政治观点分为三类：保守、自由和温和.

　　2)TheseareseveralreasonswhyIdecidedtomattendBingstonUniversity.Firstofall,thetuitionisreasonable.Secondly,theuniversityhasadeferredpaymentplan.,whichlessonstheloadofpeasantfamilieslikemine.AnotherreasonisthatBingstonhasthefinestteachersinitsgraduateprogram.Mychiefreason,however,isBingston’sprograminagriculture,mychosenfield,whichisrecognizedastheleaderinthisarea.

　　该段采用主次排列的方式,分析了作者决定上Bingston大学的原因.

　　3)AccordingtoMr.Li,thefifteenstudentsofhiscLASSfallintothreegroups.Sevenofthemworkhardandstudywell.Theyalwaysgetgoodmarksinexaminationsandareoftenpraisedbytheteachers.Licallsthem“goodstudents”.Themonitor,thesecretaryoftheYouthLeague,andthecaptainofthecLASSvolleyballteam,arequickinfindingoutwhattheirfellowstudentsareinterestedinorwhattheyshoulddoasacollective.Theyalwaysorganizeproperactivitiesatthepropertime.SoLicallsthem“goodorganizers”.FourotherstudentsareverykindtotheircLASSmates,alwaysreadytolendthemahelpinghand.TheyhelptocleanthecLASSroomandthecorridorevenwhentheyarenotonduty.Lisaysthattheyare“goodcomrades”.“Whataboutyourself