The meaning of a word can change in the course of time. Changes of lexical meanings can be proved by comparing contexts of different times. Transfer of the meaning is called lexico-semantic word-building. In such cases the outer aspect of a word does not change.

The causes of semantic changes can be extra-linguistic and linguistic, e.g. the change of the lexical meaning of the noun «pen» was due to extra-linguistic causes. Primarily « pen» comes back to the Latin word «penna» (a feather of a bird). As people wrote with goose pens the name was transferred to steel pens which were later on used for writing. Still later any instrument for writing was called « a pen».

On the other hand causes can be linguistic, e.g. the conflict of synonyms when a perfect synonym of a native word is borrowed from some other language one of them may specialize in its meaning, e.g. the noun «tide» in Old English was polisemantic and denoted «time», «season», «hour». When the French words «time», «season», «hour» were borrowed into English they ousted the word «tide» in these meanings. It was specialized and now means «regular rise and fall of the sea caused by attraction of the moon». The meaning of a word can also change due to ellipsis, e.g. the word-group «a train of carriages» had the meaning of «a row of carriages», later on «of carriages» was dropped and the noun «train» changed its meaning, it is used now in the function and with the meaning of the whole word-group.

Semantic changes have been classified by different scientists. The most complete classification was suggested by a German scientist Herman Paul in his work «Prinzipien des Sprachgeschichte». It is based on the logical principle. He distiguishes two main ways where the semantic change is gradual ( specialization and generalization), two momentary conscious semantic changes (metaphor and metonymy) and also secondary ways: gradual (elevation and degradation), momentary (hyperbole and litote).         

            SPECIALIZATION

It is a gradual process when a word passes from a general sphere to some special sphere of communication, e.g. «case» has a general meaning «circumstances in which a person or a thing is». It is specialized in its meaning when used in law (a law suit), in grammar (a form in the paradigm of a noun), in medicine (a patient, an illness). The difference between these meanings is revealed in the context.

The meaning of a word can specialize when it remains in the general usage. It happens in the case of the conflict between two absolute synonyms when one of them must specialize in its meaning to remain in the language, e.g. the native word «meat» had the meaning «food», this meaning is preserved in the compound «sweetmeats». The meaning «edible flesh» was formed when the word «food», its absolute synonym, won in the conflict of absolute synonyms (both words are native). The English verb «starve» was specialized in its meaning after the Scandinavian verb «die» was borrowed into English. «Die» became the general verb with this meaning because in English there were the noun «death» and the adjective «dead». «Starve» got the meaning «to die of hunger» .

The third way of specialization is the formation of Proper names from common nouns, it is often used in toponimics, e.g. the City - the business part of London, Oxford - university town in England, the Tower -originally a fortress and palace, later -a prison, now - a museum.

The fourth way of specialization is ellipsis. In such cases primaraly we have a word-group of the type «attribute + noun», which is used constantly in a definite situation. Due to it the attribute can be dropped and the noun can get the meaning of the whole word-group, e.g. «room» originally meant «space», this meaning is retained in the adjective «roomy» and word combinations: «no room for», «to take room», «to take no room». The meaning of the word «room « was specialized because it was often used in the combinations: «dining room», «sleeping room» which meant «space for dining» , «space for sleeping».

          GENERALIZATION

It is a process contrary to specializaton, in such cases the meaning of a word becomes more general in the course of time.

The transfer from a concrete meaning to an abstract one is most frequent, e.g. «ready» (a derivative from the verb «ridan» - «ride») meant «prepared for a ride», now its meaning is «prepared for anything». «Journey» was borrowed from French with the meaning «one day trip», now it means «a trip of any duration».

All auxiliary verbs are cases of generalization of their lexical meaning because they developed a grammatical meaning : «have», «be», «do», «shall» , «will» when used as auxiliary verbs are devoid of their lexical meaning which they have when used as notional verbs or modal verbs, e.g. cf. «I have several books by this writer» and «I have read some books by this author». In the first sentence the verb «have» has the meaning «possess», in the second sentence it has no lexical meaning, its grammatical meaning is to form Present Perfect.

           METAPHOR

 It is a transfer of the meaning on the basis of comparison. Herman Paul points out that metaphor can be based on different types of similarity:

a) similarity of shape, e.g. head (of a cabbage), bottleneck, teeth (of a saw, a comb);

b) similarity of position, e.g. foot (of a page, of a mountain), head (of a procession);

c) similarity of function, behaviour e.g. a whip (an official in the British Parliament whose duty is to see that members were present at the voting);

d) similarity of colour, e.g. orange, hazel, chestnut etc.

In some cases we have a complex similarity, e.g. the leg of a table has a similarity to a human leg in its shape, position and function.

Many metaphors are based on parts of a human body, e.g. an eye of a needle, arms and mouth of a river, head of an army.

A special type of metaphor is when Proper names become common nouns, e.g. philistine - a mercenary person, vandals - destructive people, a Don Juan - a lover of many women etc.

         METONYMY

It is a transfer of the meaning on the basis of contiguity. There are different types of metonymy:

a) the material of which an object is made may become the name of the object , e.g. a glass, boards, iron etc;

b) the name of the place may become the name of the people or of an object placed there, e.g. the House - members of Parliament, Fleet Street - bourgeois press, the White House - the Administration of the USA etc;

c) names of musical instruments may become names of musicians, e.g. the violin, the saxophone;

d) the name of some person may becom a common noun, e.g. «boycott» was originally the name of an Irish family who were so much disliked by their neighbours that they did not mix with them, «sandwich» was named after Lord Sandwich who was a gambler. He did not want to interrupt his game and had his food brought to him while he was playing cards between two slices of bread not to soil his fingers.

e) names of inventors very often become terms to denote things they invented, e.g. «watt» , «om», «rentgen» etc

f) some geographical names can also become common nouns through metonymy, e.g. holland (linen fabrics), Brussels (a special kind of carpets) , china (porcelain) , astrachan ( a sheep fur) etc.

            ELEVATION

It is a transfer of the meaning when it becomes better in the course of time, e.g. «knight» originally meant «a boy», then «a young servant», then «a military servant», then «a noble man». Now it is a title of nobility given to outstanding people; «marshal» originally meant «a horse man» now it is the highest military rank etc.

          DEGRADATION

It is a transfer of the meaning when it becomes worse in the course of time. It is usually connected with nouns denoting common people, e.g. «villain» originally meant «working on a villa» now it means «a scoundrel».

           HYPERBOLE

It is a transfer of the meaning when the speaker uses exaggeration,

e.g. «to hate»(doing something), (not to see somebody) «for ages».               

Hyperbole is often used to form phraseological units, e.g. «to make a mountain out of a molehill», «to split hairs» etc.

             LITOTE

 It is a transfer of the meaning when the speaker expresses affirmative with the negative or vica versa, e.g. not bad, no coward etc.