一、定義（Definition）
　　
（一）Introduction
             介紹
　　
When making a hypothesis（假說）or other statement， scientists must make sure that they will be understood by other researchers. Misunderstandings occur when there are different concepts of what is being discussed.
　　
A definition answers the question， “What is it?” Sometimes a definition is necessary because a word or concept has more than one meaning. For example， whether carbon is a metal or nonmetal depends on how you define carbon. At other times， a definition is required because a term is being used in a special way. For example， physicists use the terms work and energy in ways that are more specific than their common meanings. A definition should be complete enough to include all the items in the category yet narrow enough to eliminate items that do not belong. The Greek philosopher Plato once defined man as a two-legged creature that has no feathers. The problem with Plato's definition was that it did not distinguish a man from other two-legged creatures without feathers. Communication between researchers is dependent on precise definitions of substances， concepts，
processes， and ideas.
　　
　　
　　
（二）Sentence patterns
　          句   型
　
Sentence pattern 1:
An astronomer is a scientist who studies the universe.
A barometer is an instrument that measures air pressure.
Conduction is a process by which heat is transferred.
A laboratory is a place where experiments are performed.
Physics is the study of matter and energy.
A volt is a unit for measuring electrical pressure.
Sentence pattern 2:
Mercury is a liquid metal.
Asbestos is a fire-resistant mineral.
A dinosaur is a prehistoric reptile.
A monkey is a small， long -tailed primate.
　　
（三）Application Examples
            應用實例 

be 是
mean 意思是，意味著，意指
denote 表示，指
imply 意思是，意味著
be named 命名為，被稱為
Examples：
1. Printers are output devices.
打印機是輸出設備。
2. Multiprogramming means the existence of many programs in different parts of main memory at the same time.
多道程序意味著在主存儲器的不同部分同時存在著多個程序。
3. Data denotes a collection of facts that can serve as operands to computer program.
數據是指可作為計算機程序操作對象的集合。
4. A “system” implies a good mixture of integrated parts working together to form useful whole.
“系統”意指將協同工作各部分適當地綜合而成的一個有效的整體。
5. The first digital computer built in 1946 at the University of Pennsylvania was named ENIAC.
第一臺計算機是1946年在賓夕法尼亞大學建造的，命名為ENIAC。
　　
二、敘述（Describing）
　　
（一）Introduction
 
A description serves to introduce a scientist's view of the world. It may describe conditions， results of an experiment， chemical changes， physical movements， or what is seen through a telescope or microscope. A description may also tell the characteristics or distinctive features of an object―how it look， sounds， tastes， smells， works， or is produced.
 
The nature of something can be explained by describing it. For example， the concept of an atom is difficult to grasp from a definition alone， but a description of its appearance， detailing its structure and function， makes it easier to visualize.
　　
（二）Sentence patterns

The Nile River is 4，145 miles long.
Mount Everest is 8，848 meters high.
The Dead Sea is 11 miles wide.
　　
The Nile River has a length 4，145 miles.
The Sun has a surface temperature of 11，000°F.
The Grand Canyon has a depth of 5，500 feet.
　　
The color of iodine is purplish black.
The texture of sand is rough and granular.
The orbits of planets are elliptical.
Pluto is relatively small.
Blue stars are extremely hot.
Copper salts are slightly blue in aqueous solutions.
　　
（三）Application Examples

be是
be considered （to be） 被認為是，被看作
be known as 被稱為是，被認為是，即
be referred to as 稱為，叫做
be thought of as 被認為是
be regarded as 被認為是
Examples:
1. This ability to allow interrupts to interrupt previous interrupts service routines safely are referred to as nested interrupts.
允許某些中斷去中斷先前的中斷服務程序，并能正確運行的能力稱為嵌套中斷。
2. One of the most important characteristics of a computer is its capability of storing information in its memory long enough to process it.
計算機最重要的特性之一就是具有這樣一種能力，即在它的存儲器中保存信息時間長到足以對這些信息進行處理。
3. In the majority of applications the computer's capability to store and access large amounts of information plays the dominant part and is considered to be its primary characteristic.
 在大部分的應用中，計算機能夠存儲和訪問大量的信息這一特性，起了關鍵的作用，并被看成是計算機的主要特點。
 
除了定義 （Definition） 與敘述（Describing）的寫作方法以外，科技英語dissertation常用的寫作方法還有：比較（Comparing）、因果（Cause and Effect）、假設（Hypothesizing）、證明（Giving Evidence）、實驗（Experiment）、計算（Calculating）、報告（Reporting）、預測（Predicting）等。