Changes in Word Meaning
1．Types of changes
1）Extension
The extension of meaning, the opposite of restriction, means the widening of a word's sense until it covers much more than what it originally conveyed.
2）Narrowing
Narrowing of meaning, also called restriction of meaning, means that a word of wide meaning acquires a narrower, specialised sense which is applicable to only one of the objects it previously denoted.
3）Elevation
When the meaning of a word narrows toward a more favourable meaning it is called elevation
4）Degradation
Degradation means the falling of word meaning into disrepute, for one reason or another. Words once respectable or neutral may shift to a less respectable, or even derogatory meaning.
2. Causes of changes
1）Extra-linguistic factors
（1）historical reason
（2）class reason
（3）psychological reason
2）Linguistic factors
（1）shortening
（2）borrowing
（3）analogy
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