# Glossary ```{glossary} attribute name Attribute sets are a collection of key/value pairs. The attribute name is the key. 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/ ("Nix packages"). NixOS Linux distribution based on Nix and Nixpkgs. Read /nɪks oʊ ɛs/ ("Niks Oh Es"). package name TODO reproducible Reproducibility would guarantee exactly the same results no matter **when** or **on what machine** you run the command. ```