&gt; Because sign language is the most literal thing you can think of. If I look at someone and point to them, then point to someone else, what do you suppose that means? The only issue is local dialect&#x2F;slang which is easy enough to figure out.<p>I asked someone who was studying ASL about the differences between sign languages. She pointed out that they <i>do</i> commonly have different signs which might be very abstract and non-literal, often because they arose in different schools for deaf people (or different regions with a very high incidence of deafness) in earlier eras.<p>However, some of the sign languages have some etymological relationship with one another, especially French Sign Language (LSF)<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;French_Sign_Language" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;French_Sign_Language</a><p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sign_language#Classification" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sign_language#Classification</a><p>Those relationships might be something that reinforces the impression that all sign languages are inherently related, but there are also sign language isolates that don&#x27;t have an etymological relationship to other sign languages (although if they&#x27;ve had later contact with other sign languages, they could have loan vocabulary or other contact influences).<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Category:Sign_language_isolates" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Category:Sign_language_isolate...</a><p>Edit: I don&#x27;t mean to suggest that people who know different sign languages couldn&#x27;t communicate at all, but I expect that someone who knows one wouldn&#x27;t be able to understand a signed conversation between native signers of an unrelated one.