Abstract: English lexicon changes faster than grammar or pronunciation. People always create new words to express their different views. In the course of the development of language，old words die out，a fresh ones are added，and existing ones change their meanings. The paper concerns about the semantic change of words from a lexical perspective and probe into the causes and the formations of semantic change. Through analysis of the semantic change from different respects，some practical values come to rise: it is quite instrumental for English learners to attain a more complete understanding of English word meaning. In the end, this paper will analyze the internal and external reasons of semantic changes and the forms of semantic change based on English vocabulary from a lexical perspective. Therefore，this paper would place more emphasis on how the semantic change occurs and as well as what influences might impact upon English language learning.
Key words: semantic; change; lexical
1. Causes of Semantic Change
Semantic change is very difficult to describe or explain. It is unlikely that scholars will ever be able to predict the directions in which particular words will change their meanings. The concrete linguistic contexts might control the word meaning in reality. Besides，the shifts of attitudes or the language users’ psychology might also cause some words socially differentiated. As for the external factors，the historical，social and internet may also have great impacts upon semantic change of word meaning in one way or another.
Contexts in which a word lives in do influence or change its meaning more often than not. For instance，the omission of a word may lead to a change in meaning of the other words. Modifiers may be omitted with an example from English，which maybe the word “undertaker”. It once meant“one who undertakes an energetic promoter.” one translation of the twenty---third psalm began: “the Lord is my undertaker.” A common context in which the word was used that of funeral undertaker; funeral then was omitted，and until the morticians thought they could sweeten the trade with a new name，the chief context for undertaker was for people who assist in the obsequies for the dead. Therefore，it is obvious to see the linguistic context that does impact word meaning. Regarding psychological factors，we often refer to the mind of language users. To some extent, it could bring about semantic changes. Psychological factors in semantic change are a basic human tendency to emphasize and exaggerate. Taboo and euphemism are also one of the reasons that semantic change is particularly rapid according to Wang. Constant use of words may wear off their specific meaning，so that new more expressive terms are sought.
The changes of word meaning might be reflected by certain external factors such as Historical evolution，social advancement as well as the popularity of internet. Historically，changes of word meaning could be illustrated by a diachronic development of words. Although objects，concepts，ideas，etc., change in the course of time，the name is retained. Yet the meaning changes，for the object which it describes have changed .For example，“parliament”dates back to speech in old French.
Though its evolution and alteration could not be detected，its referent could remain till today. Social factors can be political，economic，scientific and technological respects，etc. ，which all strongly affect the change of word meaning more or less. Among other things，the impacts exerted by internet have been undoubtedly an attribution to it. At present，Many new words were introduced online，e. g. furkid (a pet treated as though it were one’s child) ，hyper---parenting (a child---rearing style in which parents are intensely involved in managing，scheduling，and enriching all aspects of their children’s live) as well as Gaga (derived from a famous pop singer star’s name Lady Ga Ga，referring to be crazyabout something or somebody) .
2. Formations of Semantic Change
2.1 Generalization and specialization
Generalization also called extension refers to the widening of word meaning. It is a process by which a word which originally had a specialized meaning has now become generalized or has extracted to cover a broader and often less definite concept. For example，“thing”，used to mean “a public assembly”or “a council”in Anglo---Saxon times，now can refer to any object or event. On the contrary，specialization means the narrowing of word meaning. In other words，a word used to denote a more general meaning becomes restricted in its application and conveys a special concept in present day in English. For example，deer is a typical instance. In Shakespeare’s time，the sentences “rats and mice and such small deer” the “deer” obviously designates “animal”in general. “Barbarian”was originally a vague designation for a “foreigner of any kind”，and later was specialized to mean as“uncivilized person”. Another example is the word “girl”，which covered the meaning of young people in old English ，now is restricted to mean young person of female in modern English only.
2.2Amelioration and pejoration
Amelioration and pejoration deal with the change of de-notational changes of word meaning. Amelioration is a process where the meaning of a word takes a turn for the better. A typical example is the word “inn”，which used to refer to the small motel along sides of the roads，now are adopted by some grand hotel as their brands such as the famous one of “Holiday Inn” . It is obvious to find the meaning of inn has been improved. Moreover，the English word “marshal ” once meant “horse fender” but was elevated in time to mean “officer of highest rank”. The word “minister”used to mean “attendant or servant” but now its meaning is shifted to “person at the head of a department of the state”.Pejoration，also called degradation，is the opposite of the amelioration. Examples are sufficient to be supplied. The word“knave” once meant only “boy” but then comes to be denoted to a term of abuse. All of the words “villain”“chul”and “boor”once meant merely “farmer worker”，however，no doubt because of the city---slicker’s habitual contempt for his unsophisticated country cousin， all have likewise turned to purely insults . It is interesting to notice that the degradation of word meaning occurs more frequently than the elevation of word meaning，which is perhaps due to the fact that unpleasant experiences or feelings are more easily to ingrain in people’s minds compared to those pleasing things to some extent.
In the domain of semantic change discussion，transference refers to the metaphorical usage，something like the rhetoric devices. All cases of development of change of meaning are based on some association. In fact，semantic changes involve meaning shift from literal meaning to figurative meaning. So the process of a new changing of meaning is termed transference . People always use figures of speech to express this kind of semantic changes. Traditionally，figurative language has been described in terms of categories such as simile，metaphor，euphemism and so on. Suffice to provide an example with metaphor，which is the commonest of all semantic change using the source field to define the target，i. e. ，the mouth of a river; here the mouth implies the place where a river enters a sea. Other examples could be “Love is a journey” “life is a train” “an geris container”，for their literal meaning of journey，train and container has been transferred into metaphorical meanings.
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