diff --git a/New-sign-system-(v0.18).md b/New-sign-system-(v0.18).md
index a2cb852..74a5070 100644
--- a/New-sign-system-(v0.18).md
+++ b/New-sign-system-(v0.18).md
@@ -62,6 +62,16 @@ public long getIntervalTicks() - Returns the interval time in ticks (20/s)
 
 ## List of signs by their group
 
+/ = or
+
+() = Optional
+
+{} = Nonterminal
+
+{}* = Nonterminal may occur multiple times with "," as a separator, e.g. "{Item ID}*" -> "IRON_SWORD,APPLE,STICK"
+
+everything else = Terminal
+
 | Group   | Name         | 2nd line syntax         | 3rd line syntax         |
 |---------|--------------|-------------------------|-------------------------|
 | Button  | ActionBar    | {MSG ID}                | N/A                     |
@@ -93,6 +103,6 @@ public long getIntervalTicks() - Returns the interval time in ticks (20/s)
 | Rocker  | Door         | N/A                     | N/A                     |
 | Rocker  | Trigger      | {ID of fired T trigger} | N/A                     |
 | Windup  | Command      | {Command script ID}     | {Delay in sec.},OP/CONSOLE/DEFAULT |
-| Windup  | Drop         |
+| Windup  | Drop         | {Item ID}               | {Stack size}(,{Drop rate})
 | Windup  | Mob          | {Mob ID = fired M trigger} | {Delay in sec.},{Amount}(,{external mob plugin tag}) |
 | Windup  | Redstone     | {Delay in decisec.}     | ({Repeats}|0)           |