1． The definition of a word：

　　A word is a minimal free form of language which has a given sound and meaning and syntactic function.

　　2． Sound and Meaning

　　There is no logical or intrisinc connection between a sound and what it refers to. The relation between sound and meaning is almost always arbitrary or conventional. The same language can use the same sound to mean different things and the different languages use different sounds to refer to the same thing.

　　3． Sound and Form

　　The written form of English is not an acurate representation of the spoken form.There are different causes of the differences between sounds and forms in the English language.

　　1）The English alphabet was adopted from the Romans, which does not employ the system of one single letter to stand for one sound.

　　2）The early scribes deliberately changed spelling of words to make a line even or for easier recogniton.

　　3） Dictionaries help to fix the spelling of words

　　4） English has borrowed many words from other languages, which may not have been assimilated .

　　4． Vocabulary

　　All the words in a language are termed as vocabulary. However, vocabulary can also be used to refer to all the words in a book, or in a particular historical period of time, or in a dialet, or in a particular discipline, or even to all the words that a person possesses.

　　5． Classification of Words

　　Words can be classified into the basic word stock and nonbasic word stock by use frequence, into content words and functional words by notion and into native words and borrowed words by origin.

　　1）The Characteristics of the Basic Word Stock

　　（1） All national character

　　（2）stability

　　（3）productivity

　　（4）polysemy

　　（5）collocability

　　2）The Characteristics of borrowed words

　　（1）Denizens: the early borrowed words which have been assimilated and conformed to the English way of pronounciation and spelling.

　　（2）Aliens: the borrowed words which have retained the foreign way of pronounciation or spelling and have not been assimilated into the English language.

　　（3）Translation-loans: the words and expressions which are formed from the existing English materials, but modelled on the patterns of another language.

　　（4）Semantic loans: Words which have not been borrowed with reference to the form, but to the meanings.

　　3） Roles Played by the native words.

　　Native words are limited in number, but form the core of the English language. Native words are often neutral in style and frequent in use