The first group of causes of development of new meanings is traditionally termed historical or extra-linguistic.

Different kinds of changes in a nation's social life, in its culture, knowledge, technology, arts lead to gaps appearing in the vocabulary which beg to be filled. Newly created objects, new concepts and phenomena must be named. Languages are powerfully affected by social, political, economic, cultural and technical change. The influence of those factors upon linguistic phenomena is studied by sociolinguistics. It shows that social factors can influence even structural features of linguistic units: terms of science, for instance, have a number of specific features as compared to words used in other spheres of human activity.

We already know of two ways for providing new names for newly created concepts: making new words (word-building) and borrowing foreign ones. One more way of filling such vocabulary gaps is by applying some old word to a new object or notion.

The word being a linguistic realization of notion, it changes with the progress of human consciousness. This process is reflected in the development of lexical meaning. As the human mind achieves an ever more exact understanding of the world of reality and the objective relationships that characterize it, the notions become more and more exact reflections of real things. The history of the social, economic and political life of the people, the progress of culture and science bring about changes in notions and things influencing the semantic aspect of language. For instance, The word space meant "extent of time or distance" or "intervening distance". Alongside this meaning a new meaning developed "the limitless and indefinitely great expanse in which all material objects are located". The phrase outer space was quickly ellipted into space. Cf. spacecraft, spacesuit, space travel, etc.

The extra-linguistic motivation is sometimes obvious, but some cases are not as straightforward as they may look. The word bikini may be taken as an example. Bikini, a very scanty two-piece bathing suit worn by women, is named after Bikini atoll in the Western Pacific but not because it was first introduced on some fashionable beach there. Bikini appeared at the time when the atomic bomb tests by the US in the Bikini atoll were fresh in everybody's memory. The associative field is emotional referring to the "atomic" shock the first bikinis produced.

The tendency to use technical imagery is increasing in every language, thus the expression to spark off in chain reaction is almost international. Live wire "one carrying electric current" used figuratively about a person of intense energy seems purely English, though.

Other international expressions are black box and feed-back. Black box formerly a term of aviation and electrical engineering is now used figuratively to denote any mecha-nism performing intricate functions or any unit of which we know the effect but not the components or principles of action.

Feed-back a cybernetic term meaning "the return of a sample of the output of a system or process to the input, especially with the purpose of automatic adjustment and control" is now widely used figuratively meaning "response".

When the first textile factories appeared in England, the old word mill was applied to these early industrial enterprises. In this way, mill (a Latin borrowing of the first century B. C.) added a new meaning to its former meaning "a building in which com is ground into flour". The new meaning was "textile factory".

A similar case is the word carriage which had (and still has) the meaning "a vehicle drawn by horses", but, with the first appearance of railways in England, it received a new meaning, that of "a railway car".

The history of English nouns describing different parts of a theatre may also serve as a good illustration of how well-established words can be used to denote newly-created objects and phenomena. The words stalls, box, pit, circle had existed for a long time before the first theatres appeared in England. With their appearance, the gaps in the vocabulary were easily filled by these widely used words which, as a result, developed new meanings. It is of some interest to note that the Ukrainian language found a different way of filling the same gap: in Ukrainian, all the parts of the theatre are named by borrowed words: партер, ложа, амфітеатр, бельетаж.

The changes of notions and things named go hand in hand. They are conditioned by changes in the economic, social, political and cultural history of the people, so that the extralinguistic causes of semantic change might be conveniently subdivided in accordance with these. Social relationships are at work in the cases of elevation and pejoration of meaning where the attitude of the upper classes to their social inferiors determined the strengthening of emotional tone among the semantic components of the word.

Sociolinguistics also teaches that power relationships are reflected in vocabulary changes. In all the cases of pejoration such as boor, churl, villain, etc., it was the ruling class that imposed evaluation. The opposite is rarely the case. One example deserves attention though: sir + -ly used to mean "masterful" and now sirly means "rude in a bad-tempered way".