diff --git a/number/number.go b/number/number.go
index 87c5fdb..587b96e 100644
--- a/number/number.go
+++ b/number/number.go
@@ -6,6 +6,27 @@ import (
 	"sourcecode.social/reiver/go-opt"
 )
 
+// Number represents a JSON number literal as defined by IETF RFC-8259.
+//
+//	number = [ minus ] int [ frac ] [ exp ]
+//	
+//	decimal-point = %x2E       ; .
+//	
+//	digit1-9 = %x31-39         ; 1-9
+//	
+//	e = %x65 / %x45            ; e E
+//	
+//	exp = e [ minus / plus ] 1*DIGIT
+//	
+//	frac = decimal-point 1*DIGIT
+//	
+//	int = zero / ( digit1-9 *DIGIT )
+	
+//	minus = %x2D               ; -
+//	
+//	plus = %x2B                ; +
+//	
+//	zero = %x30                ; 0
 type Number struct {
 	opt.Optional[string]
 }