Merge pull request #263 from fricklerhandwerk/nomenclature

codify terminology

CONTRIBUTING.md

@@ -183,3 +183,37 @@ Collect links at the end of each section, which are delimited by headings.
 
 [Here is a discussion of different line wrapping styles.]: https://web.archive.org/web/20220519121408/https://mtsknn.fi/blog/4-1-wrapping-styles-for-markdown-prose-and-code-comments/
 [reference links]: https://github.github.com/gfm/#reference-link
+
+### Terminology
+
+To avoid confusion around all the things called Nix, always use the following terms with capitalization as given.
+
+- Nix
+
+  Build system and package manager.
+
+  Read /nɪks/ ("Niks").
+
+- Nix language
+
+    Programming language to declare packages and configurations for Nix.
+
+  - Nix expression
+
+    Expression written in the Nix language.
+
+  - Nix file
+
+    File (`.nix`) containing a Nix expression.
+
+- Nixpkgs
+
+  Software distribution built with Nix.
+
+  Read /nɪks ˈpækɪʤɪz/ ("Niks packages").
+
+- NixOS
+
+  Linux distribution based on Nix and Nixpkgs.
+
+  Read /nɪks oʊ ɛs/ ("Niks Oh Es").