Sign language
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Sign languages are languages that use the visual-manual modality to convey meaning, instead of spoken words. Sign languages are expressed through manual articulation in combination with non-manual markers. Sign languages are full-fledged natural languages with their own grammar and lexicon. Sign languages are not universal and are usually not mutually intelligible, although there are also similarities among different sign languages.
Two men and a woman signing American Sign Language (2008)
Juan Pablo Bonet, Reducción de las letras y arte para enseñar a hablar a los mudos ("Reduction of letters and art for teaching mute people to speak") (Madrid, 1620)
Chirogram from Chirologia, 1644
Sign language relief sculpture on a stone wall: "Life is beautiful, be happy and love each other", by Czech sculptor Zuzana Čížková on Holečkova Street in Prague-Smíchov, by a school for the deaf
Charles-Michel de l'Épée
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Charles-Michel de l'Épée was a philanthropic educator of 18th-century France who has become known as the "Father of the Deaf".
L'Épée's signes méthodiques are represented on his funeral monument in the Church of St. Roch, Paris