1# Configuration Syntax {#sec-configuration-syntax}
2
3The NixOS configuration file `/etc/nixos/configuration.nix` is actually
4a *Nix expression*, which is the Nix package manager's purely functional
5language for describing how to build packages and configurations. This
6means you have all the expressive power of that language at your
7disposal, including the ability to abstract over common patterns, which
8is very useful when managing complex systems. The syntax and semantics
9of the Nix language are fully described in the [Nix
10manual](https://nixos.org/nix/manual/#chap-writing-nix-expressions), but
11here we give a short overview of the most important constructs useful in
12NixOS configuration files.
13
14```{=include=} sections
15config-file.section.md
16abstractions.section.md
17modularity.section.md
18```