diff --git a/knowledge.md b/knowledge.md
index f57227bf2..bae11a813 100644
--- a/knowledge.md
+++ b/knowledge.md
@@ -2,10 +2,13 @@
 
 - [[go]] wikipedia.org
 - [[information]] about [[everything]].
+- The theoretical or practical understanding of a subject.
+  - Some of it is [[useful]].
 
 
 [//begin]: # "Autogenerated link references for markdown compatibility"
 [go]: go "Go"
 [information]: information "Information"
 [everything]: everything "Everything"
+[useful]: useful "Useful"
 [//end]: # "Autogenerated link references"
\ No newline at end of file