nix/doc/manual/src/expressions/builtins-prefix.md

Built-in Functions

This section lists the functions built into the Nix expression evaluator. (The built-in function derivation is discussed above.) Some built-ins, such as derivation, are always in scope of every Nix expression; you can just access them right away. But to prevent polluting the namespace too much, most built-ins are not in scope. Instead, you can access them through the builtins built-in value, which is a set that contains all built-in functions and values. For instance, derivation is also available as builtins.derivation.

derivation attrs; builtins.derivation attrs

derivation is described in its own section.