diff --git a/parser/phrase.go b/parser/phrase.go
index 5962d84..c2a4578 100644
--- a/parser/phrase.go
+++ b/parser/phrase.go
@@ -306,7 +306,7 @@ func (parser *parsingOperation) parsePhraseCommand () (
 
 	// determine semantic role of phrase
 	if command.kind == ArgumentKindString {
-		kind = PhraseKindCallExternal
+		kind = PhraseKindArbitrary
 		
 	} else if command.kind == ArgumentKindIdentifier {
 		identifier := command.value.(Identifier)
diff --git a/parser/tree.go b/parser/tree.go
index 6f247cc..9f0e6d4 100644
--- a/parser/tree.go
+++ b/parser/tree.go
@@ -231,19 +231,46 @@ type Dereference struct {
 type PhraseKind int
 
 const (
-	PhraseKindCall = iota
-	PhraseKindCallExternal
+	// [name]
+	PhraseKindCall PhraseKind = iota
+	
+	// ["name"]
+	PhraseKindArbitrary
+	
+	// [+] [-]
 	PhraseKindOperator
+	
+	// [= x y]
 	PhraseKindAssign
+	
+	// [loc x]
 	PhraseKindReference
+	
+	// [cast x T]
 	PhraseKindCast
+
+	// [defer]
 	PhraseKindDefer
+	
+	// [if c]
 	PhraseKindIf
+	
+	// [elseif]
 	PhraseKindElseIf
+	
+	// [else]
 	PhraseKindElse
+	
+	// [switch]
 	PhraseKindSwitch
+	
+	// [case]
 	PhraseKindCase
+	
+	// [while c]
 	PhraseKindWhile
+	
+	// [for x y z]
 	PhraseKindFor
 )