Everything rolls on, nothing stays still.
Heraclitus, 6th century B.C.
English language has more than 2000 years of history in which several invaders, migrants, tradesmen and also cultural and technological influences have contributed to create present day English.
English has undertaken the most remarkable diachronic changes amongst other major European languages, so that the language in which the epic poem Beowulf was written, called Old English (700-1000), is now not accessible for English speakers.  The changes are also synchronic, in fact at any given time we can notice differences amongst the huge varieties of English spoken in different regions or countries.
Language change is at work also in the present and affects every part of the language: vocabulary, pronunciation, orthography and grammar.
The sounds of a language changes in a slow and slightly noticeable way. For example, the words ‘latter’ and ‘ladder’ are pronounced in the same way by most young and some adult American people, but 50 years ago the two words were pronounced differently.
Grammar change is also a slow process. Nowadays the distinction between will and shall is used only by some upper-class British or the distinction between ‘who’ and ‘whom’ is on the wane. An interesting example is the use of “historic perfect”2, a phenomenon that is rising amongst the young people in UK. They use the past perfect for referring to events that usually require the past perfect. This tendency has the purpose of signalling to the listener that one part of the speech is more interesting and appealing.
English vocabulary is constantly changing in the use or in the meaning of the words and in preference for one word or phrase over another. It is also noticeable with the introduction of new words which fulfil the need to adapt the language to new discovers, ideas and inventions, as for example telephone, astronaut, quark. At other times, changes take place...