sign_language

the deaf. To speak the sign language you must do

movement of the hands, arms or body, and show the speaker's thoughts.
Signing is also done by persons who can hear, but cannot physically speak. Hundreds of sign languages are in use around the world. Some sign languages have legal recognition.
A common misconception is that all sign languages are the same worldwide or that sign language is international.

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 transfer words from a spoken to a signed language.
In 1620, Juan Pablo Bonet published ‘Reduction of letters and art for teaching mute people to speak’ in Madrid. It is considered the first modern treatise of sign language phonetics, setting out a method of oral education for deaf people and a manual alphabet.

many advantages. First of all, it is quite rich to

show the most important meanings that exist in all languages. As a result, a sign language can be used to discuss any topic, from very simple to difficult. Also, it is more systematic than spoken languages. Additionally, the visual form of sign language makes a connection between form and meaning.
A sign language also has some disadvantages. Firstly, it is very complex, so it takes much time to learn the language. Secondly, it can be easily misunderstood in other countries because each sign language has similarities but at the same time one sign has different meaning in other cultures. Thirdly, it can not be totally used in the darkness because it is a visually based type of communication. And fourthly, a sign language can not be used by people who are physically disabled or do not have some parts of their body.