What are the unique characteristics of sign languages that make them so fascinating? What have recent researchers discovered about them, and what do these findings tell us about human language more generally? This thematic and geographic overview examines more than forty sign languages from around the world. It begins by investigating how sign languages have survived and been transmitted for generations, and then goes on to analyse the common characteristics shared by most sign languages: for example, how the use of the visual system affects grammatical structures. The final section describes...