Does Elixir have a language specification?

There's no formal specification. Here are some things to look at, that describe the language and might be useful:

• Syntax Reference - available only in master docs.
• Kernel.SpecialForms - these are the things that are provided "by the language" and cannot be changed - more or less like keywords in other languages. Everything else is macros/functions implemented in Elixir.
• Kernel - this module is imported by default and can be viewed as the "base" of the language - everything from here can be locally changed by importing, though.