【正文】 rent forms occur owing to different sound environment. These minimal meaningful units are known as morphemes. In other words, the morpheme is the amallest functioning unit in the position of words2 Morphemes are abstract units, which are realized in speech by discrete units known as morphs. They are actual spoken , minimal carriers of meaning. The morpheme is to the morph what a phoneme is to a phone.3 These morphemes coincide with words as they can stand by themselves and function freely in a sentence. Words of this kind are called monomorphemic words. 4 Some morphemes, however, are realized by more than one morph according to their position in a word. Such alternative morphs are known as allomorphs.5 There are cases where the allomorphs of the plural morpheme are realized by the change of an internal vowel or by zero morph. 6 Free Morphemes which are independent of other morphemes are considered to be free. These morphemes have plete meanings in themselves and can be used as free grammatical units in sentences. They are identical with root words, as each of them consists of a single free root, we might as well say that free morphemes are free roots.7 Bound Morphemes which cannot occur as separate words are bound. They are so named because they are bound to other morphemes to form words. social, economic and politicalchanges(24%)。They accordingly fall into eight principal groups, which can be grouped into an Eastern set: BaltoSlavic , IndoIranian , Armenian and Albanian 。 the Angles, the Saxons, and the Jutes, thus known as AngloSaxon words.24 Apart from the characteristics mentioned of the basic word stock, in contrast to borrowed words, native words have two other features:Neutral in style. they are not stylistically specific.Stylistically, natives words are neither formal nor informal whereas the words borrowed from French or Latin are literary and learned, thus appropiate in formal style.Frequent in use. Native words are most frequently used in everyday speech and writing.25 Words taken over from foreign languages are known as borrowed words or loan words or borrowings in simple terms. It is estimated that English borrowings constitute 80 percent of the modem English vocabulary. The English language is noted for the remarkable plexity and heterogeneity of its vocabulary because of its extensive borrowings26 Aliens are borrowed words which have retained their original pronunciation and spelling. These words are immediately recognizable as foreign in origin.27 Semanticloans. Words of this category are not borrowed with reference to the form. But their meanings are borrowed. In other words, English has borrowed a new meaning for an existing word in the language. Chapter 2 The development of the English vocabulary 1 It is assumed that the world has approximately 3, 000 (some put it 5, 000 ) languages, which can be grouped into roughly 300 language families on the basis of similarities in their basic word stock and grammar.2 The IndoEuropean is one of them. It is made up of most of the languages of Europe, the Near East, and India. 3 (3) a unit of meaning。Chapter 1 Basic concepts of words and vocabulary 1 The definition of a word prises the following points:(1) a minimal free form of a language。(2) a sound unity。(4) a form that can function alone in a sentence. A word is a minimal free form of a language that has a given sound and meaning and syntactic function. 2 Sound and Meaning:symbolic connection is almost always arbitrary and conventional.A dog is called a dog not because the sound and the three letters that make up the word just automatically suggest the animal in question.3 Old English, the speech of the time was represented very much more faithfully in writing than it is today. The internal reason for this is that the English alphabet was adopted from the Romans, which does not have a separate letter to represent each sound in the language so that some letters must do double duty or work together in bination. Another reason is that the pronunciation has changed more rapidly than spelling over the years, and in some cases the two have drawn far apart.A third reason is that some of the differences were created by the early scribes.Finally es the borrowing, which is an important channel of enriching the English vocabulary.5 Vocabulary: All the words in a language make up its vocabulary.Not only can it refer to the total number of the words in a language, but it can stand for all the words used in a particular historical period. We also use it to refer to all the words of a given dialect, a given book, a given discipline and the words possessed by an individual person. The general estimate of the presentday English vocabulary is over million words. 6 Words may fall into the basic word stock and nonbasic vocabulary by use frequency, into content words and functional words by notion, and into native words and borrowed words by origin.7 The basic word stock is the foundation of the vocabulary accumulated over centuries and forms the mon core of the language. Though words of the basic word stock constitute a small percentage of the English vocabulary, yet it is the most important part of it. These words have obvious characteristics.8 All national character. Words of the basic word stock denote the most mon things and phenomena of the world around us, which are indispensable to all the people who speak the languageNatural phenomena/Human body and relations/Names of plants and animals/Action, size, domain, state/Numerals, pronouns, prepositions, conjunctions 9 Stability. Words of the basic word stock have been in use for centuries.10 Productivity . Words of the basic word stock are mostly root words or monosyllabic words. They can each be used alone, and at the same time can form new words with other roots and affixes.11 Polysemy. Words belonging to the