English is a living language, which means it changes over time. New words are constantly entering the language, evidenced by the Oxford English Dictionary’s policy of adding English words to their lexicon quarterly. There are many avenues for a word to enter into use.
New words may be coined from existing words. Compound words are words constructed from two existing words that when put together, form a new meaning. Portmanteaus are words constructed from the blending of two existing words. Back-formations are words that are derived by changing or omitting a prefix or suffix.
New words may be loaned or borrowed from other languages or dialects. Sometimes these new words are anglicized, sometimes they retain their original spelling. The exact meaning may or may not survive the transition from the source language to the English language.
New words are often incorporated into the main body of the English language from regional English or dialects. Words and phrases that were peculiar to a certain place are more and more often used by those who hail from outside the region, due to the global effect of mass media and the internet.
When new technologies enter society, new words to describe that technology accompany them.
This has been especially true with the advent of the internet. A related situation is the rise of the use of acronyms. Many acronyms are pronounced as a word, and as the acronym is repeatedly used, it may evolve into the form of an actual word.
Another interesting linguistic phenomenon is the functional shift, which occurs when the majority of people using a word define it in a new way. This may occur when a large group of English speakers don’t quite understand the original meaning of a word or prefer one definition to another by a great margin.
Finally, some new words are pure inventions. Writers often invent words to suit their purposes. If these words are coined by a famous writer, or if the invention strikes the fancy of the public, the word may enter general usage. In the end, whether or not a new word is added to the English language depends on its use by average English speakers.