The Celts are those people that at one time spoke a Celtic language, including the modern descendants of those people. The word Celt is derived from the Greek keltoi, meaning "secret people," and is the reason Celt is pronounced with a hard "C" or "K" sound. The Celts are a wide-ranging group of people with diverse geographic and cultural backgrounds.
Around 3 BCE, most of Europe was Celtic, and all of these people spoke a common language, Old Celtic. The empire stretched from the Iberian Peninsula to the Scottish Highlands, the Black Sea, and into central Italy. At that time, the massive size of the Celtic empire led to the development of two distinct groups of Celts. Those people near the Iberian Peninsula were known as the Celtiberi, and those who lived near the Black Sea were the Galtae. Eventually, the invasion of the Romans, Saxons, Angles and Jutes forced the Celtic people to the north and west of Europe. As the Celts dispersed, the language fragmented as well.
The first wave of Celts in the British Isles spoke what is called Goidelic, which eventually led to three Gaelic languages — Irish, Scottish Gaelic and Manx. These three languages were primarily spoken in Ireland, the Isle of Man and Scotland. The second wave of Celtic immigrants spoke the Brythonic form of the language, which led to Welsh and Cornish, and survived also as Breton, which was spoken in Brittany, a region in France.
Today, many people identify themselves as descendants of the Celts, and are proud of their Celtic heritage. Ireland's effort to prevent Gaelic from dying out completely was spurred on by a Constitutional referendum in 1937 making Gaelic the official language. Street signs, advertisements and television broadcasts are frequently presented in Irish as well as English.
The Celtic literary tradition began in the 8th century. Celts also developed their own style of art and music. The art often incorporates curved lines and knotwork and has complex symbolic meanings, frequently drawing on literary themes.
Pictish art was created in Scotland from the 5th to the 9th centuries. Its images, typically carved in stone, include animals, people, Biblical motifs, and crosses with intricate scrollwork. Some of these images can be seen in the Book of Kells, a manuscript transcribed by Celtic monks in 800 CE, which is considered by some to be “Ireland's finest national treasure.”