diff --git a/Convention/[Symbolization]/Internal/Functional.cs b/Convention/[Symbolization]/Internal/Functional.cs
index e8c8f93..692bcda 100644
--- a/Convention/[Symbolization]/Internal/Functional.cs
+++ b/Convention/[Symbolization]/Internal/Functional.cs
@@ -6,11 +6,13 @@ using System.Threading.Tasks;
 
 namespace Convention.Symbolization.Internal
 {
-    public class Function : Variable
+    public abstract class Function : Variable
     {
-        public Variable Invoke(Variable[] parameters)
+        public readonly FunctionSymbol FunctionInfo;
+        public abstract Variable Invoke(Variable[] parameters);
+        public Function(string symbolName, Type returnType, Type[] parameterTypes, Modification[] modifiers)
         {
-
+            FunctionInfo = new(symbolName, returnType, parameterTypes, modifiers);
         }
     }
 
diff --git a/Convention/[Symbolization]/Internal/Modification.cs b/Convention/[Symbolization]/Internal/Modification.cs
index b2e4562..b93e692 100644
--- a/Convention/[Symbolization]/Internal/Modification.cs
+++ b/Convention/[Symbolization]/Internal/Modification.cs
@@ -6,7 +6,7 @@ using System.Threading.Tasks;
 
 namespace Convention.Symbolization.Internal
 {
-    public class Modification : Variable
+    public abstract class Modification : Variable
     {
     }
 }
diff --git a/Convention/[Symbolization]/Internal/Structure.cs b/Convention/[Symbolization]/Internal/Structure.cs
new file mode 100644
index 0000000..93a5f08
--- /dev/null
+++ b/Convention/[Symbolization]/Internal/Structure.cs
@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Convention.Symbolization.Internal
+{
+    public sealed class Structure : Variable
+    {
+        public readonly string Name;
+        private Dictionary<VariableSymbol, Variable> VariableSymbolAndDefaultValue;
+
+        private Structure(string name)
+        {
+            this.Name = name;
+        }
+        public Structure(string name, Dictionary<VariableSymbol, Variable> variableSymbolAndDefaultValue)
+        {
+            this.Name = name;
+            this.VariableSymbolAndDefaultValue = variableSymbolAndDefaultValue;
+        }
+
+        public override object Clone()
+        {
+            Structure target = new(Name);
+            foreach (var pair in VariableSymbolAndDefaultValue)
+            {
+                target.VariableSymbolAndDefaultValue[pair.Key] = pair.Value;
+            }
+            return target;
+        }
+    }
+}
diff --git a/Convention/[Symbolization]/Internal/Variable.cs b/Convention/[Symbolization]/Internal/Variable.cs
index 305777b..d525b88 100644
--- a/Convention/[Symbolization]/Internal/Variable.cs
+++ b/Convention/[Symbolization]/Internal/Variable.cs
@@ -6,9 +6,9 @@ using System.Threading.Tasks;
 
 namespace Convention.Symbolization.Internal
 {
-    public class Variable
+    public abstract class Variable : ICloneable
     {
-
+        public abstract object Clone();
     }
 
     public readonly struct VariableSymbol