The recorded history of sign language in Western societies starts in the 17th century, as a visual language or method of communication, although references to forms of communication using hand gestures date back as far as 5th century BC Greece. Sign language is composed of a system of conventional gestures, mimic, hand signs and finger spelling, plus the use of hand positions to represent the letters of the alphabet. Signs can also represent complete ideas or phrases, not only individual words. Most sign languages are natural languages, different in construction from oral languages used in proximity to them, and are employed mainly by deaf people in order to communicate. Many sign languages have developed independently throughout the world, and no first sign language can be identified. Both signed systems and manual alphabets have been found worldwide. Until the 19th century, most of what we know about historical sign languages is limited to the manual alphabets (fingerspelling systems) that were invented to facilitate transfer of words from an oral to a sign language, rather than documentation of the sign language itself. History of known sign languages One of the earliest written references to a sign language is from the fifth century BC, in Plato's Cratylus, where Socrates says: "If we hadn't a voice or a tongue, and wanted to express things to one another, wouldn't we try to make signs by moving our hands, head, and the rest of our body, just as dumb people do at present?" In the Middle Ages, monastic sign languages were used by a number of religious orders in Europe since at least the 10th century. These are not true "sign languages", however, but well-developed systems of gestural communication. In Native American communities prior to 1492, it seems that Plains Indian Sign Language existed as an extensive lingua franca used for trade and possibly ceremonies, story-telling and also daily communication by deaf people. Accounts of such signing indicate these languages were fairly complex, as ethnographers such as Cabeza de Vaca described detailed communications between them and Native Americans that were conducted in sign. In the 1500s, a Spanish expeditionary, Cabeza de Vaca, observed natives in the western part of modern-day Florida using signs, and in the mid-16th century Coronado mentioned that communication with the Tonkawa using signs was possible without a translator.. The earliest concrete reference to sign language in Britain is from the wedding of