Etymology is the study of the origins of words. The etymology of a word is its linguistic history. For example, the word etymology comes to us from the Ancient Greek language. It is composed of two parts: the Greek word etymon, which means "the true sense of a word", combined with the Greek element logia, which means "doctrine, study". Combining these two parts gives us "the study of the true sense of words", which can be said to be the 'meaning' of the word etymology.

Language Changes:
Over time, languages evolve. This is due to slow changes in pronunciation, vocabulary and grammar that naturally occur over long periods of time. The Old English word modor became the Middle English moder which eventually became the modern English mother. One language may split into two different languages when speakers are separated by physical or cultural barriers for extended periods. When two speakers have noticeable differences in speech but can still understand each other, they are said to be speaking different dialects. When they can no longer mutually understand one another, then they are speaking different languages.

Language Families:
Linguists divide the languages of the world, past and present, into various language families. English belongs to a family of languages called the Indo-European Language Family, which includes Greek, French, Russian, Hindi, German, Irish, and many other tongues of Europe and Asia. It is theorized that thousands of years ago all Indo-European languages had a common ancestor, a hypothetical protolanguage. There are many other families besides Indo-European, and there are attempts to prove relations between the different families.

Cognates:
One way that linguists prove that languages are related to one another is by using cognates. A cognate is a related word in another language. For example, the English word mother has cognates in several other Indo-European languages: Greek meter, Russian mate, German mutter, Sanskrit matri, and Irish mathair. These words all share a similar sound, and thousands of years ago they were likely all the same word in the same language.

Loanwords:
English has many words of foreign origin, which are called loanwords. A great deal of the English vocabulary is made up of French and Latin loanwords, which were added by the French-speaking Norman invaders who conquered England in the 11th century AD. Other languages with which English speakers come into contact add to the vocabulary as well.

To learn more about the interesting world of etymology and linguistics, try the University of Rochester's linguistics links.