1 files changed, 10 insertions, 2 deletions
diff --git a/docs/type_system/union.md b/docs/type_system/union.md
index 2c4be2d..79c4987 100644
--- a/docs/type_system/union.md
+++ b/docs/type_system/union.md
@@ -5,11 +5,19 @@
 ```text
 Union_class `alias Enum[.container; .transient]
 
-Union[Union_class; TYPE.symbol; ...]
+Union[Union_class; Collection[TYPE.SYMBOL]]
 ```
 
+# Alias
+
+```text
+Tag[Collection[TYPE.SYMBOL]] `alias Union[.container; Collection[TYPE.SYMBOL]]
+```
+
+## Tag Example
+
 ```text
-u : Union[I64.a; I64.b; I64.c] $ (.c : 5) // defaults to Union[.container; ...]
+u : Tag[I64.a; I64.b; I64.c] $ (.c : 5)
 
 # u {
     .c {[c] c ... }