A．Pure technical terms(specialized technical terms):used only in certain disciplines，fields and branches of learning，for example，hydroxide氢氧化合物，diode二极管，isotope同位素．

B．General-purpose technical terms: used in more or less the same sense in a great variety of disciplines，fields and branches of learning，for example，frequency频率，density密度，energy能量，magnetism磁性，feedback反馈，transmission传送．

C．Semi-technical words: used in different disciplines，fields and branches of learning．For instance，the primary meaning of“feed”is喂养，but it can mean加电，供水，输送，加载，进刀or电源in different contexts or fields．The word “service”can carry the sense of运转，操作，维修，设备or使用in different technical fields instead of the basic meaning服务．

D．Abstract nouns: derived from verbs or adjectives，for example，insulate—insulation，expand—expansion，move—movement，leak—leakage，stable—stability，humid—humidity and so on．The use of abstract nouns serves to achieve concision and formalness which characterize Scientific English．

E．Words with affixation:some examples with prefix hydra-:hydra-beating，hydrability，hydracids，hydra-cyclone，hydragoga，etc．and some words with suffix-meter: barometer，chronometer，thermometer，spectrometer，micrometer，etc．The extensive use of affixation is intended to name the multitude of new concepts that keep springing up each day in the world of science and technology．

F．Abbreviations:forexample，RADCM(radarcountermeasure)，CTF(certificate)，LADAR(laser radar)，AWACS(airborne warning and control system)，and PPC(program planning and control)．The extensive use of abbreviations is also intended to meet the requirements of concision and economy in Scientific English．

G．Common words: used in the same way as in everyday English．

2)Lexical characteristics

A．Some scientific English words are monotonous and stable in meaning and usage as compared with ordinary English．For example ，“make”is seldom used in its basic meaning of做，制造，but often has the following two collocations: one is make + action noun，for example ，“make a calculation” ，“make a change” ，“make a correction” ，“make a measurement”etc．，the other make + direct object + indirect object，for example ，“make something done” ，“make something a tool” etc．．

B．Abstract nouns denoting actions or states are extensively used．They are mostly derived from verbs or adjectives，such as “transmission” ，“evaluation” ，and“resistance” ．This is known as“the trend of nominalization”in English for Science and Technology．“The trend of nominalization”is intended to achieve the concision and formality of expression，and the simplicity of structure，for example ，“the utilization of salinity power by reverse electro-dialysis and other methods”(盐动力是通过逆电渗发和别的方法来利用的)is commonly used instead of“Salinity power is utilized by reverse electro-dialysis and other methods” ．

C．Scientific English is characterized by formalness and solemnity．It tends to use formal words instead of informal or colloquial words in terms of its diction．Here are five pairs of synonyms below，the first one is an informal word while the second one is a formal word which is likely to occur in English for Science and Technology．

send—transmit　change—convert　enough—sufficient

　better—superior　use up—consume

D．A feature“the continuous use of nouns”in English for Science and Technology means that a headword is modified by several nouns．This is also referred to as“Expanded Noun Modifiers” ．“The continuous use of noun”can effectively simplify sentential structure．

power transmission relay system = a relay system for power transmission

　送电中继系统

illumination intensity determination = determination of the intensity of illumination

　照明强度测定

E．The frequent use of connectives such as conjunctions or prepositions．This is due to the emphasis on logical relations and logical reasoning in English for Science and Technology．

6．2. 1 Lexical Characteristics词法特点

6．2. 1　Lexical Characteristics词法特点