diff --git a/lib/libthr/libthr.3 b/lib/libthr/libthr.3
--- a/lib/libthr/libthr.3
+++ b/lib/libthr/libthr.3
@@ -52,6 +52,12 @@
 and
 .Lb libc ;
 all three components must be built from the same source tree.
+Together, they constitute the base C runtime environment of
+.Fx ,
+running on top of the
+.Fx
+kernel.
+.Pp
 Mixing
 .Li libc
 and