diff --git a/gcc/elna-diagnostic.cc b/gcc/elna-diagnostic.cc
index e19eea5..27f60bb 100644
--- a/gcc/elna-diagnostic.cc
+++ b/gcc/elna-diagnostic.cc
@@ -36,6 +36,10 @@ namespace gcc
         {
             return "String";
         }
+        else if (is_array_type(type))
+        {
+            return "array";
+        }
         else
         {
             return "<<unknown-type>>";
diff --git a/gcc/elna-generic.cc b/gcc/elna-generic.cc
index 96c9435..852463a 100644
--- a/gcc/elna-generic.cc
+++ b/gcc/elna-generic.cc
@@ -282,6 +282,36 @@ namespace gcc
         this->current_expression = NULL_TREE;
     }
 
+    void generic_visitor::visit(source::type_definition *definition)
+    {
+        tree tree_type = build_type(definition->body());
+
+        if (tree_type == NULL_TREE)
+        {
+            return;
+        }
+        location_t definition_location = get_location(&definition->position());
+        tree definition_tree = build_decl(definition_location, TYPE_DECL,
+                get_identifier(definition->identifier().c_str()), tree_type);
+        auto result = this->symbol_map.insert({ definition->identifier(), definition_tree });
+
+        if (result.second)
+        {
+            DECL_CONTEXT(definition_tree) = this->main_fndecl;
+            variable_chain.append(definition_tree);
+
+            auto declaration_statement = build1_loc(definition_location, DECL_EXPR,
+                    void_type_node, definition_tree);
+            append_to_statement_list(declaration_statement, &this->current_statements);
+        }
+        else
+        {
+            error_at(definition_location,
+                    "type '%s' already declared in this scope",
+                    definition->identifier().c_str());
+        }
+    }
+
     tree generic_visitor::build_type(source::type_expression& type)
     {
         if (source::basic_type_expression *basic_type = type.is_basic())
@@ -306,6 +336,12 @@ namespace gcc
             {
                 return elna_string_type_node;
             }
+            auto symbol = this->symbol_map.find(basic_type->base_name());
+
+            if (symbol != this->symbol_map.end())
+            {
+                return TREE_TYPE(symbol->second);
+            }
         }
         else if (source::array_type_expression *array_type = type.is_array())
         {
@@ -371,39 +407,47 @@ namespace gcc
         this->current_expression = symbol->second;
     }
 
+    void generic_visitor::visit(source::array_access_expression *expression)
+    {
+        expression->base().accept(this);
+        tree designator = this->current_expression;
+
+        expression->index().accept(this);
+        tree index = this->current_expression;
+
+        tree element_type = TREE_TYPE(TREE_TYPE(designator));
+
+        this->current_expression = build4_loc(get_location(&expression->position()),
+                ARRAY_REF, element_type, designator, index, NULL_TREE, NULL_TREE);
+    }
+
     void generic_visitor::visit(source::assign_statement *statement)
     {
-        auto lvalue = this->symbol_map.find(statement->lvalue());
+        statement->lvalue().accept(this);
+
+        auto lvalue = this->current_expression;
         auto statement_location = get_location(&statement->position());
 
-        if (lvalue == this->symbol_map.end())
-        {
-            error_at(statement_location,
-                    "variable '%s' not declared in the current scope",
-                    statement->lvalue().c_str());
-            return;
-        }
         statement->rvalue().accept(this);
 
-        if (TREE_CODE(lvalue->second) == CONST_DECL)
+        if (TREE_CODE(lvalue) == CONST_DECL)
         {
             error_at(statement_location, "cannot modify constant '%s'",
-                    statement->lvalue().c_str());
+                    statement->lvalue().is_variable()->name().c_str());
             this->current_expression = error_mark_node;
             return;
         }
-        if (TREE_TYPE(this->current_expression) != TREE_TYPE(lvalue->second))
+        if (TREE_TYPE(this->current_expression) != TREE_TYPE(lvalue))
         {
             error_at(statement_location,
-                    "cannot assign value of type %s to variable '%s' of type %s",
+                    "cannot assign value of type %s to variable of type %s",
                     print_type(TREE_TYPE(this->current_expression)),
-                    statement->lvalue().c_str(),
-                    print_type(TREE_TYPE(lvalue->second)));
+                    print_type(TREE_TYPE(lvalue)));
             this->current_expression = error_mark_node;
             return;
         }
         auto assignment = build2_loc(statement_location, MODIFY_EXPR,
-                void_type_node, lvalue->second, this->current_expression);
+                void_type_node, lvalue, this->current_expression);
 
         append_to_statement_list(assignment, &this->current_statements);
         this->current_expression = NULL_TREE;
diff --git a/gcc/elna-tree.cc b/gcc/elna-tree.cc
index ccdabe9..9b0be60 100644
--- a/gcc/elna-tree.cc
+++ b/gcc/elna-tree.cc
@@ -23,6 +23,12 @@ namespace gcc
             && TYPE_MAIN_VARIANT(TREE_TYPE(type)) == char_type_node;
     }
 
+    bool is_array_type(tree type)
+    {
+        gcc_assert(TYPE_P(type));
+        return TREE_CODE(type) == ARRAY_TYPE;
+    }
+
     tree tree_chain_base::head()
     {
         return first;
diff --git a/gcc/elna1.cc b/gcc/elna1.cc
index fdadfcf..4d36b6f 100644
--- a/gcc/elna1.cc
+++ b/gcc/elna1.cc
@@ -197,7 +197,7 @@ static tree elna_langhook_builtin_function(tree decl)
 
 static bool elna_langhook_global_bindings_p(void)
 {
-    gcc_unreachable();
+    return false;
 }
 
 static tree elna_langhook_pushdecl(tree decl ATTRIBUTE_UNUSED)
diff --git a/include/elna/gcc/elna-generic.h b/include/elna/gcc/elna-generic.h
index 2b29efa..83e6aa3 100644
--- a/include/elna/gcc/elna-generic.h
+++ b/include/elna/gcc/elna-generic.h
@@ -40,8 +40,10 @@ namespace gcc
         void visit(source::string_literal *string) override;
         void visit(source::binary_expression *expression) override;
         void visit(source::constant_definition *definition) override;
+        void visit(source::type_definition *definition) override;
         void visit(source::declaration *declaration) override;
         void visit(source::variable_expression *expression) override;
+        void visit(source::array_access_expression *expression) override;
         void visit(source::assign_statement *statement) override;
         void visit(source::if_statement *statement) override;
         void visit(source::while_statement *statement) override;
diff --git a/include/elna/gcc/elna-tree.h b/include/elna/gcc/elna-tree.h
index bc39de6..031e786 100644
--- a/include/elna/gcc/elna-tree.h
+++ b/include/elna/gcc/elna-tree.h
@@ -23,6 +23,7 @@ namespace gcc
 {
     void init_ttree();
     bool is_string_type(tree type);
+    bool is_array_type(tree type);
 
     class tree_chain_base
     {
diff --git a/include/elna/source/ast.h b/include/elna/source/ast.h
index ba2aa2b..efd573b 100644
--- a/include/elna/source/ast.h
+++ b/include/elna/source/ast.h
@@ -37,6 +37,7 @@ namespace source
     class declaration;
     class constant_definition;
     class procedure_definition;
+    class type_definition;
     class call_statement;
     class compound_statement;
     class assign_statement;
@@ -49,6 +50,7 @@ namespace source
     class basic_type_expression;
     class array_type_expression;
     class variable_expression;
+    class array_access_expression;
     template<typename T>
     class number_literal;
     class char_literal;
@@ -62,6 +64,7 @@ namespace source
         virtual void visit(declaration *) = 0;
         virtual void visit(constant_definition *) = 0;
         virtual void visit(procedure_definition *) = 0;
+        virtual void visit(type_definition *) = 0;
         virtual void visit(call_statement *) = 0;
         virtual void visit(compound_statement *) = 0;
         virtual void visit(assign_statement *) = 0;
@@ -74,6 +77,7 @@ namespace source
         virtual void visit(basic_type_expression *) = 0;
         virtual void visit(array_type_expression *) = 0;
         virtual void visit(variable_expression *) = 0;
+        virtual void visit(array_access_expression *) = 0;
         virtual void visit(number_literal<std::int32_t> *) = 0;
         virtual void visit(number_literal<double> *) = 0;
         virtual void visit(number_literal<bool> *) = 0;
@@ -89,6 +93,7 @@ namespace source
         virtual void visit(declaration *) override;
         virtual void visit(constant_definition *definition) override;
         virtual void visit(procedure_definition *definition) override;
+        virtual void visit(type_definition *definition) override;
         virtual void visit(call_statement *statement) override;
         virtual void visit(compound_statement *statement) override;
         virtual void visit(assign_statement *statement) override;
@@ -99,8 +104,9 @@ namespace source
         virtual void visit(binary_expression *expression) override;
         virtual void visit(unary_expression *expression) override;
         virtual void visit(basic_type_expression *) override;
-        virtual void visit(array_type_expression *) override;
+        virtual void visit(array_type_expression *expression) override;
         virtual void visit(variable_expression *) override;
+        virtual void visit(array_access_expression *expression) override;
         virtual void visit(number_literal<std::int32_t> *) override;
         virtual void visit(number_literal<double> *) override;
         virtual void visit(number_literal<bool> *) override;
@@ -358,6 +364,20 @@ namespace source
         virtual ~procedure_definition() override;
     };
 
+    class type_definition : public definition
+    {
+        type_expression *m_body;
+
+    public:
+        type_definition(const struct position position, const std::string& identifier,
+                type_expression *expression);
+        virtual void accept(parser_visitor *visitor) override;
+
+        type_expression& body();
+
+        virtual ~type_definition() override;
+    };
+
     /**
      * Call statement.
      */
@@ -393,9 +413,49 @@ namespace source
         virtual ~compound_statement() override;
     };
 
+    class designator_expression : public expression
+    {
+    public:
+        virtual variable_expression *is_variable();
+        virtual array_access_expression *is_array_access();
+
+    protected:
+        designator_expression(const struct position position);
+    };
+
+    class variable_expression : public designator_expression
+    {
+        std::string m_name;
+
+    public:
+        variable_expression(const struct position position, const std::string& name);
+        virtual void accept(parser_visitor *visitor) override;
+
+        const std::string& name() const;
+
+        variable_expression *is_variable() override;
+    };
+
+    class array_access_expression : public designator_expression
+    {
+        designator_expression *m_base;
+        expression *m_index;
+
+    public:
+        array_access_expression(const struct position position, designator_expression *base, expression *index);
+        virtual void accept(parser_visitor *visitor) override;
+
+        designator_expression& base();
+        expression& index();
+
+        array_access_expression *is_array_access() override;
+
+        ~array_access_expression() override;
+    };
+
     class assign_statement : public statement
     {
-        std::string m_lvalue;
+        designator_expression *m_lvalue;
         expression *m_rvalue;
 
     public:
@@ -404,11 +464,11 @@ namespace source
          * \param lvalue Left-hand side.
          * \param rvalue Assigned expression.
          */
-        assign_statement(const struct position position, const std::string& lvalue,
+        assign_statement(const struct position position, designator_expression *lvalue,
                 expression *rvalue);
         virtual void accept(parser_visitor *visitor) override;
 
-        std::string& lvalue();
+        designator_expression& lvalue();
         expression& rvalue();
 
         virtual ~assign_statement() override;
@@ -537,17 +597,6 @@ namespace source
         const std::string& string() const;
     };
 
-    class variable_expression : public expression
-    {
-        std::string m_name;
-
-    public:
-        variable_expression(const struct position position, const std::string& name);
-        virtual void accept(parser_visitor *visitor) override;
-
-        const std::string& name() const;
-    };
-
     class binary_expression : public expression
     {
         expression *m_lhs;
diff --git a/include/elna/source/result.h b/include/elna/source/result.h
index f30938d..77eafe4 100644
--- a/include/elna/source/result.h
+++ b/include/elna/source/result.h
@@ -69,36 +69,5 @@ namespace source
 
         std::string what() const override;
     };
-
-    struct type_mismatch final : public error
-    {
-        /**
-         * Kind of the operation on the type.
-         */
-        enum class operation
-        {
-            dereference,
-            argument,
-            arithmetic,
-            comparison,
-            condition,
-            assignment
-        };
-
-        /**
-         * \param name Given type.
-         * \param kind Kind of the operation on the type.
-         * \param path Source file name.
-         * \param position Operation position.
-         */
-        type_mismatch(std::shared_ptr<const type> got, operation kind, const char *path,
-                const struct position position);
-
-        std::string what() const override;
-
-    private:
-        std::shared_ptr<const type> got;
-        operation kind;
-    };
 }
 }
diff --git a/source/ast.cc b/source/ast.cc
index 2b5b86d..32cec0b 100644
--- a/source/ast.cc
+++ b/source/ast.cc
@@ -25,6 +25,11 @@ namespace source
         definition->body().accept(this);
     }
 
+    void empty_visitor::visit(type_definition *definition)
+    {
+        definition->body().accept(this);
+    }
+
     void empty_visitor::visit(call_statement *statement)
     {
         for (auto& argument : statement->arguments())
@@ -91,14 +96,21 @@ namespace source
     {
     }
 
-    void empty_visitor::visit(array_type_expression *)
+    void empty_visitor::visit(array_type_expression *expression)
     {
+        expression->base().accept(this);
     }
 
     void empty_visitor::visit(variable_expression *)
     {
     }
 
+    void empty_visitor::visit(array_access_expression *expression)
+    {
+        expression->base().accept(this);
+        expression->index().accept(this);
+    }
+
     void empty_visitor::visit(number_literal<std::int32_t> *)
     {
     }
@@ -332,6 +344,27 @@ namespace source
         }
     }
 
+    type_definition::type_definition(const struct position position, const std::string& identifier,
+            type_expression *body)
+        : definition(position, identifier), m_body(body)
+    {
+    }
+
+    void type_definition::accept(parser_visitor *visitor)
+    {
+        visitor->visit(this);
+    }
+
+    type_expression& type_definition::body()
+    {
+        return *m_body;
+    }
+
+    type_definition::~type_definition()
+    {
+        delete m_body;
+    }
+
     block::block(const struct position position, std::vector<definition *>&& definitions,
             std::vector<declaration *>&& declarations,
             statement *body)
@@ -415,8 +448,13 @@ namespace source
         return m_string;
     }
 
+    designator_expression::designator_expression(const struct position position)
+        : expression(position)
+    {
+    }
+
     variable_expression::variable_expression(const struct position position, const std::string& name)
-        : expression(position), m_name(name)
+        : designator_expression(position), m_name(name)
     {
     }
 
@@ -430,6 +468,42 @@ namespace source
         return m_name;
     }
 
+    variable_expression *variable_expression::is_variable()
+    {
+        return this;
+    }
+
+    array_access_expression::array_access_expression(const struct position position,
+            designator_expression *base, expression *index)
+        : designator_expression(position), m_base(base), m_index(index)
+    {
+    }
+
+    void array_access_expression::accept(parser_visitor *visitor)
+    {
+        visitor->visit(this);
+    }
+
+    expression& array_access_expression::index()
+    {
+        return *m_index;
+    }
+
+    designator_expression& array_access_expression::base()
+    {
+        return *m_base;
+    }
+
+    array_access_expression *array_access_expression::is_array_access()
+    {
+        return this;
+    }
+
+    array_access_expression::~array_access_expression()
+    {
+        delete m_base;
+    }
+
     binary_expression::binary_expression(const struct position position, expression *lhs,
             expression *rhs, const unsigned char operation)
         : expression(position), m_lhs(std::move(lhs)), m_rhs(std::move(rhs))
@@ -590,15 +664,25 @@ namespace source
         visitor->visit(this);
     }
 
-    assign_statement::assign_statement(const struct position position, const std::string& lvalue,
+    assign_statement::assign_statement(const struct position position, designator_expression *lvalue,
             expression *rvalue)
         : statement(position), m_lvalue(lvalue), m_rvalue(rvalue)
     {
     }
 
-    std::string& assign_statement::lvalue()
+    variable_expression *designator_expression::is_variable()
     {
-        return m_lvalue;
+        return nullptr;
+    }
+
+    array_access_expression *designator_expression::is_array_access()
+    {
+        return nullptr;
+    }
+
+    designator_expression& assign_statement::lvalue()
+    {
+        return *m_lvalue;
     }
 
     expression& assign_statement::rvalue()
diff --git a/source/lexer.ll b/source/lexer.ll
index 16d40d2..de17ce0 100644
--- a/source/lexer.ll
+++ b/source/lexer.ll
@@ -67,6 +67,10 @@ array                   {
 of                      {
                             return yy::parser::make_OF(this->location);
                         }
+type                    {
+                            return yy::parser::make_TYPE(this->location);
+                        }
+
 true                    {
                             return yy::parser::make_BOOLEAN(true, this->location);
                         }
diff --git a/source/parser.yy b/source/parser.yy
index 9b5abfc..b7c11bb 100644
--- a/source/parser.yy
+++ b/source/parser.yy
@@ -63,7 +63,7 @@
 %token <std::string> STRING "string"
 %token <bool> BOOLEAN
 %token IF WHILE DO
-%token CONST VAR PROCEDURE ARRAY OF
+%token CONST VAR PROCEDURE ARRAY OF TYPE
 %token BEGIN_BLOCK END_BLOCK
 %token LEFT_PAREN RIGHT_PAREN LEFT_SQUARE RIGHT_SQUARE SEMICOLON DOT COMMA
 %token GREATER_EQUAL LESS_EQUAL LESS_THAN GREATER_THAN NOT_EQUAL EQUALS
@@ -87,6 +87,7 @@
 %type <elna::source::expression *> expression pointer summand factor address comparand;
 %type <std::vector<elna::source::expression *>> expressions actual_parameter_list;
 %type <elna::source::variable_expression *> variable_expression;
+%type <elna::source::designator_expression *> designator_expression;
 %type <elna::source::compound_statement *> compound_statement;
 %type <elna::source::assign_statement *> assign_statement;
 %type <elna::source::call_statement *> call_statement;
@@ -95,26 +96,31 @@
 %type <elna::source::statement *> statement;
 %type <std::vector<elna::source::statement *>> statements optional_statements;
 %type <elna::source::procedure_definition *> procedure_definition;
-%type <std::vector<elna::source::procedure_definition *>> procedure_definitions
-    procedure_definition_part;
+%type <std::vector<elna::source::procedure_definition *>> procedure_definitions procedure_definition_part;
+%type <elna::source::type_definition *> type_definition;
+%type <std::vector<elna::source::type_definition *>> type_definitions type_definition_part;
 %type <elna::source::block *> block;
 %%
-program: constant_definition_part procedure_definition_part variable_declaration_part statement DOT
+program:
+    type_definition_part constant_definition_part procedure_definition_part variable_declaration_part statement DOT
         {
-            std::vector<elna::source::definition *> definitions($1.size() + $2.size());
+            std::vector<elna::source::definition *> definitions($1.size() + $2.size() + $3.size());
             std::vector<elna::source::definition *>::iterator definition = definitions.begin();
 
-            for (auto& constant : $1)
+            for (auto& type : $1)
+            {
+                *definition++ = type;
+            }
+            for (auto& constant : $2)
             {
                 *definition++ = constant;
             }
-            for (auto& procedure : $2)
+            for (auto& procedure : $3)
             {
                 *definition++ = procedure;
             }
             driver.tree = std::make_unique<elna::source::program>(elna::source::position{},
-                 std::move(definitions), std::move($3),
-                 std::move($4));
+                 std::move(definitions), std::move($4), std::move($5));
         }
 block: constant_definition_part variable_declaration_part statement
         {
@@ -170,7 +176,7 @@ compound_statement: BEGIN_BLOCK optional_statements END_BLOCK
             $$ = new elna::source::compound_statement(elna::source::make_position(@1));
             std::swap($$->statements(), $2);
         }
-assign_statement: IDENTIFIER ASSIGNMENT expression
+assign_statement: designator_expression ASSIGNMENT expression
         {
             $$ = new elna::source::assign_statement(elna::source::make_position(@1), $1, $3);
         }
@@ -201,7 +207,7 @@ pointer:
     | boolean_literal { $$ = $1; }
     | character_literal { $$ = $1; }
     | string_literal { $$ = $1; }
-    | variable_expression { $$ = $1; }
+    | designator_expression { $$ = $1; }
     | LEFT_PAREN expression RIGHT_PAREN { $$ = std::move($2); }
 summand:
     factor { $$ = std::move($1); }
@@ -280,8 +286,14 @@ expressions:
             $$.emplace($$.cbegin(), $1);
         }
     | expression { $$.emplace_back(std::move($1)); }
-variable_expression: IDENTIFIER
-        { $$ = new elna::source::variable_expression(elna::source::make_position(@1), $1); }
+variable_expression:
+    IDENTIFIER { $$ = new elna::source::variable_expression(elna::source::make_position(@1), $1); }
+designator_expression:
+	variable_expression LEFT_SQUARE expression RIGHT_SQUARE
+        {
+            $$ = new elna::source::array_access_expression(elna::source::make_position(@1), $1, $3);
+        }
+    | variable_expression { $$ = $1; }
 statement:
     compound_statement { $$ = $1; }
     | assign_statement { $$ = $1; }
@@ -324,9 +336,8 @@ variable_declaration_part:
     | VAR variable_declarations SEMICOLON { std::swap($$, $2); }
 constant_definition: IDENTIFIER EQUALS integer_literal
         {
-            $$ = new elna::source::constant_definition(elna::source::make_position(@1),
-                $1, $3); 
-        };
+            $$ = new elna::source::constant_definition(elna::source::make_position(@1), $1, $3); 
+        }
 constant_definitions:
     constant_definition COMMA constant_definitions
         {
@@ -336,7 +347,21 @@ constant_definitions:
     | constant_definition { $$.emplace_back(std::move($1)); }
 constant_definition_part:
     /* no constant definitions */ {}
-    | CONST constant_definitions SEMICOLON { std::swap($$, $2); };
+    | CONST constant_definitions SEMICOLON { std::swap($$, $2); }
+type_definition: IDENTIFIER EQUALS type_expression
+        {
+            $$ = new elna::source::type_definition(elna::source::make_position(@1), $1, $3);
+        }
+type_definitions:
+    type_definition COMMA type_definitions
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | type_definition { $$.emplace_back(std::move($1)); }
+type_definition_part:
+    /* no type definitions */ {}
+    | TYPE type_definitions SEMICOLON { std::swap($$, $2); }
 formal_parameter_list:
     LEFT_PAREN RIGHT_PAREN {}
     | LEFT_PAREN variable_declarations RIGHT_PAREN { std::swap($$, $2); }
diff --git a/source/result.cc b/source/result.cc
index 8bd5947..a7b493d 100644
--- a/source/result.cc
+++ b/source/result.cc
@@ -24,7 +24,7 @@ namespace source
 
     name_collision::name_collision(const std::string& name, const char *path,
             const struct position current, const struct position previous)
-        : error(path, current), name(name), previous(previous)
+        : error(path, current), previous(previous), name(name)
     {
     }
 
@@ -32,16 +32,5 @@ namespace source
     {
         return "Name '" + name + "' was already defined";
     }
-
-    type_mismatch::type_mismatch(std::shared_ptr<const type> got, operation kind,
-            const char *path, const struct position position)
-        : error(path, position), kind(kind), got(got)
-    {
-    }
-
-    std::string type_mismatch::what() const
-    {
-        return "Type cannot be used here.";
-    }
 }
 }
diff --git a/source/types.cc b/source/types.cc
index 356dc54..993a38c 100644
--- a/source/types.cc
+++ b/source/types.cc
@@ -48,7 +48,7 @@ namespace source
     }
 
     procedure_type::procedure_type(std::vector<std::shared_ptr<const type>> arguments, const std::size_t byte_size)
-        : arguments(std::move(arguments)), type(byte_size)
+        :type(byte_size), arguments(std::move(arguments))
     {
     }