diff --git a/src/operation/index.md b/src/operation/index.md
index 6ecf834..10ebd85 100644
--- a/src/operation/index.md
+++ b/src/operation/index.md
@@ -4,7 +4,7 @@ Synit uses the Linux kernel as a hardware abstraction and virtualisation layer.
 
 All processes in the system are arranged into a [supervision
 tree](../glossary.md#supervision-tree), conceptually rooted at the [system
-bus](./system-bus.md) (NB. not at PID 1).
+bus](./system-bus.md).
 
 ```ditaa system-supervision-tree
               +----------------------------------+
@@ -28,6 +28,11 @@ bus](./system-bus.md) (NB. not at PID 1).
 
 ```
 
+While `init` is PID 1, and thus the root of the tree of processes according to the kernel, it
+is *not* the root of the supervision tree. The `init` process, acting as management daemon for
+the *kernel* from Synit's perspective, is "supervised" by the system bus like all other
+services. The supervision tree is a Synit concept, not a Linux concept.
+
 <!--
 Here's an example of `ps` output from a Synit prototype running on a mobile phone: