diff --git a/include/cppast/cpp_entity_kind.hpp b/include/cppast/cpp_entity_kind.hpp
index e0e88a6..0e4ecfb 100644
--- a/include/cppast/cpp_entity_kind.hpp
+++ b/include/cppast/cpp_entity_kind.hpp
@@ -28,6 +28,9 @@ namespace cppast
 
         variable_t,
 
+        function_parameter_t,
+        function_t,
+
         count,
     };
 
diff --git a/include/cppast/cpp_function.hpp b/include/cppast/cpp_function.hpp
new file mode 100644
index 0000000..afb6a9f
--- /dev/null
+++ b/include/cppast/cpp_function.hpp
@@ -0,0 +1,215 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#ifndef CPPAST_CPP_FUNCTION_HPP_INCLUDED
+#define CPPAST_CPP_FUNCTION_HPP_INCLUDED
+
+#include <cppast/cpp_entity_container.hpp>
+#include <cppast/cpp_storage_specifiers.hpp>
+#include <cppast/cpp_variable_base.hpp>
+
+namespace cppast
+{
+    /// A [cppast::cpp_entity]() modelling a function parameter.
+    class cpp_function_parameter final : public cpp_variable_base
+    {
+    public:
+        /// \returns A newly created and registered function parameter.
+        static std::unique_ptr<cpp_function_parameter> build(
+            const cpp_entity_index& idx, cpp_entity_id id, std::string name,
+            std::unique_ptr<cpp_type> type, std::unique_ptr<cpp_expression> def = nullptr);
+
+    private:
+        cpp_function_parameter(std::string name, std::unique_ptr<cpp_type> type,
+                               std::unique_ptr<cpp_expression> def)
+        : cpp_variable_base(std::move(name), std::move(type), std::move(def))
+        {
+        }
+
+        cpp_entity_kind do_get_entity_kind() const noexcept override;
+    };
+
+    /// The kinds of function bodies of a [cppast::cpp_function_base]().
+    enum cpp_function_body_kind
+    {
+        cpp_function_declaration, //< Just a declaration.
+        cpp_function_definition,  //< Regular definition.
+        cpp_function_defaulted,   //< Defaulted definition.
+        cpp_function_deleted,     //< Deleted definition.
+    };
+
+    /// Base class for all entities that are functions.
+    ///
+    /// It contains arguments and common flags.
+    class cpp_function_base : public cpp_entity,
+                              public cpp_entity_container<cpp_function_base, cpp_function_parameter>
+    {
+    public:
+        /// \returns The [cppast::cpp_function_body_kind]().
+        cpp_function_body_kind body_kind() const noexcept
+        {
+            return body_;
+        }
+
+        /// \returns A [ts::optional_ref]() to the [cppast::cpp_expression]() that is the given `noexcept` condition.
+        /// \notes If this returns `nullptr`, the function has the implicit noexcept value (i.e. none, unless it is a destructor).
+        /// \notes There is no way to distinguish between `noexcept` and `noexcept(true)`.
+        type_safe::optional_ref<const cpp_expression> noexcept_condition() const noexcept
+        {
+            return type_safe::opt_cref(noexcept_expr_.get());
+        }
+
+        /// \returns Whether the function has an ellipsis.
+        bool is_variadic() const noexcept
+        {
+            return variadic_;
+        }
+
+    protected:
+        /// Builder class for functions.
+        ///
+        /// Inherit from it to provide additional setter.
+        template <typename T>
+        class basic_builder
+        {
+        public:
+            /// \effects Sets the name.
+            basic_builder(std::string name) : function(new T(name))
+            {
+            }
+
+            /// \effects Adds a parameter.
+            void add_parameter(std::unique_ptr<cpp_function_parameter> parameter)
+            {
+                static_cast<cpp_function_base&>(*function).add_child(std::move(parameter));
+            }
+
+            /// \effects Marks the function as variadic.
+            void is_variadic()
+            {
+                static_cast<cpp_function_base&>(*function).variadic_ = true;
+            }
+
+            /// \effects Sets the noexcept condition expression.
+            void noexcept_condition(std::unique_ptr<cpp_expression> cond)
+            {
+                static_cast<cpp_function_base&>(*function).noexcept_expr_ = std::move(cond);
+            }
+
+            /// \effects Sets the [cppast::cpp_function_body_kind]().
+            void body_kind(cpp_function_body_kind kind)
+            {
+                static_cast<cpp_function_base&>(*function).body_ = kind;
+            }
+
+            /// \effects Registers the function.
+            /// \returns The finished function.
+            std::unique_ptr<T> finish(const cpp_entity_index& idx, cpp_entity_id id)
+            {
+                idx.register_entity(std::move(id), type_safe::cref(*function));
+                return std::move(function);
+            }
+
+        protected:
+            basic_builder()           = default;
+            ~basic_builder() noexcept = default;
+
+            std::unique_ptr<T> function;
+        };
+
+        cpp_function_base(std::string name)
+        : cpp_entity(std::move(name)), body_(cpp_function_declaration), variadic_(false)
+        {
+        }
+
+    private:
+        std::unique_ptr<cpp_expression> noexcept_expr_;
+        cpp_function_body_kind          body_;
+        bool                            variadic_;
+    };
+
+    /// A [cppast::cpp_entity]() modelling a C++ function.
+    /// \notes This is not a member function,
+    /// use [cppast::cpp_member_function]() for that.
+    /// It can be a `static` function of a class,
+    /// or a `friend`, however.
+    class cpp_function final : public cpp_function_base
+    {
+    public:
+        /// Builds a [cppast::cpp_function]().
+        class builder : public cpp_function_base::basic_builder<cpp_function>
+        {
+        public:
+            /// \effects Sets the name and return type.
+            builder(std::string name, std::unique_ptr<cpp_type> return_type)
+            {
+                function = std::unique_ptr<cpp_function>(
+                    new cpp_function(std::move(name), std::move(return_type)));
+            }
+
+            /// \effects Sets the storage class.
+            void storage_class(cpp_storage_specifiers storage)
+            {
+                function->storage_ = storage;
+            }
+
+            /// \effects Marks the function as `constexpr`.
+            void is_constexpr()
+            {
+                function->constexpr_ = true;
+            }
+
+            /// \effects Marks the function as `friend`.
+            void is_friend()
+            {
+                function->friend_ = true;
+            }
+        };
+
+        /// \returns A reference to the return [cppast::cpp_type]().
+        const cpp_type& return_type() const noexcept
+        {
+            return *return_type_;
+        }
+
+        /// \returns The [cppast::cpp_storage_specifiers]() of the function.
+        /// \notes If it is `cpp_storage_class_static` and inside a [cppast::cpp_class](),
+        /// it is a `static` class function.
+        cpp_storage_specifiers storage_class() const noexcept
+        {
+            return storage_;
+        }
+
+        /// \returns Whether the function is marked `constexpr`.
+        bool is_constexpr() const noexcept
+        {
+            return constexpr_;
+        }
+
+        /// \returns Whether the function is a `friend` function of the parent [cppast::cpp_class]().
+        bool is_friend() const noexcept
+        {
+            return friend_;
+        }
+
+    private:
+        cpp_entity_kind do_get_entity_kind() const noexcept override;
+
+        cpp_function(std::string name, std::unique_ptr<cpp_type> ret)
+        : cpp_function_base(std::move(name)),
+          return_type_(std::move(ret)),
+          storage_(cpp_storage_class_none),
+          friend_(false),
+          constexpr_(false)
+        {
+        }
+
+        std::unique_ptr<cpp_type> return_type_;
+        cpp_storage_specifiers    storage_;
+        bool                      friend_;
+        bool                      constexpr_;
+    };
+} // namespace cppast
+
+#endif // CPPAST_CPP_FUNCTION_HPP_INCLUDED
diff --git a/include/cppast/cpp_function_types.hpp b/include/cppast/cpp_function_types.hpp
index 00ab89a..656c67e 100644
--- a/include/cppast/cpp_function_types.hpp
+++ b/include/cppast/cpp_function_types.hpp
@@ -25,14 +25,14 @@ namespace cppast
             {
             }
 
-            /// \effects Adds an argument type.
-            void add_argument(std::unique_ptr<cpp_type> arg)
+            /// \effects Adds an parameter type.
+            void add_parameter(std::unique_ptr<cpp_type> arg)
             {
-                func_->arguments_.push_back(*func_, std::move(arg));
+                func_->parameters_.push_back(*func_, std::move(arg));
             }
 
             /// \effects Adds an ellipsis, marking it as variadic.
-            void variadic()
+            void is_variadic()
             {
                 func_->variadic_ = true;
             }
@@ -53,10 +53,10 @@ namespace cppast
             return *return_type_;
         }
 
-        /// \returns An iteratable object iterating over the argument types.
-        detail::iteratable_intrusive_list<cpp_type> argument_types() const noexcept
+        /// \returns An iteratable object iterating over the parameter types.
+        detail::iteratable_intrusive_list<cpp_type> parameter_types() const noexcept
         {
-            return type_safe::ref(arguments_);
+            return type_safe::ref(parameters_);
         }
 
         /// \returns Whether or not the function is variadic (C-style ellipsis).
@@ -77,7 +77,7 @@ namespace cppast
         }
 
         std::unique_ptr<cpp_type>        return_type_;
-        detail::intrusive_list<cpp_type> arguments_;
+        detail::intrusive_list<cpp_type> parameters_;
         bool                             variadic_;
     };
 
@@ -99,14 +99,14 @@ namespace cppast
             {
             }
 
-            /// \effects Adds an argument type.
-            void add_argument(std::unique_ptr<cpp_type> arg)
+            /// \effects Adds a parameter type.
+            void add_parameter(std::unique_ptr<cpp_type> arg)
             {
-                func_->arguments_.push_back(*func_, std::move(arg));
+                func_->parameters_.push_back(*func_, std::move(arg));
             }
 
             /// \effects Adds an ellipsis, marking it as variadic.
-            void variadic()
+            void is_variadic()
             {
                 func_->variadic_ = true;
             }
@@ -133,10 +133,10 @@ namespace cppast
             return *object_type_;
         }
 
-        /// \returns An iteratable object iterating over the argument types.
-        detail::iteratable_intrusive_list<cpp_type> argument_types() const noexcept
+        /// \returns An iteratable object iterating over the parameter types.
+        detail::iteratable_intrusive_list<cpp_type> parameter_types() const noexcept
         {
-            return type_safe::ref(arguments_);
+            return type_safe::ref(parameters_);
         }
 
         /// \returns Whether or not the function is variadic (C-style ellipsis).
@@ -158,7 +158,7 @@ namespace cppast
         }
 
         std::unique_ptr<cpp_type>        class_type_, object_type_;
-        detail::intrusive_list<cpp_type> arguments_;
+        detail::intrusive_list<cpp_type> parameters_;
         bool                             variadic_;
     };
 
diff --git a/include/cppast/cpp_storage_specifiers.hpp b/include/cppast/cpp_storage_specifiers.hpp
new file mode 100644
index 0000000..fee9171
--- /dev/null
+++ b/include/cppast/cpp_storage_specifiers.hpp
@@ -0,0 +1,40 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#ifndef CPPAST_CPP_STORAGE_SPECIFIERS_HPP_INCLUDED
+#define CPPAST_CPP_STORAGE_SPECIFIERS_HPP_INCLUDED
+
+namespace cppast
+{
+    /// C++ storage class specifiers.
+    enum cpp_storage_specifiers
+    {
+        cpp_storage_class_none = 0,
+
+        cpp_storage_class_static = 1,
+        cpp_storage_class_extern = 2,
+
+        cpp_storage_class_thread_local = 4,
+    };
+
+    /// \returns Whether the [cppast::cpp_storage_specifiers]() contain `thread_local`.
+    inline bool is_thread_local(cpp_storage_specifiers spec) noexcept
+    {
+        return (spec & cpp_storage_class_thread_local) != 0;
+    }
+
+    /// \returns Whether the [cppast::cpp_storage_specifiers]() contain `static`.
+    inline bool is_static(cpp_storage_specifiers spec) noexcept
+    {
+        return (spec & cpp_storage_class_static) != 0;
+    }
+
+    /// \returns Whether the [cppast::cpp_storage_specifiers]() contain `extern`.
+    inline bool is_extern(cpp_storage_specifiers spec) noexcept
+    {
+        return (spec & cpp_storage_class_extern) != 0;
+    }
+} // namespace cppast
+
+#endif // CPPAST_CPP_STORAGE_SPECIFIERS_HPP_INCLUDED
diff --git a/include/cppast/cpp_type.hpp b/include/cppast/cpp_type.hpp
index 6540d68..c54edd0 100644
--- a/include/cppast/cpp_type.hpp
+++ b/include/cppast/cpp_type.hpp
@@ -103,7 +103,7 @@ namespace cppast
     {
     public:
         /// \returns A newly created builtin type.
-        std::unique_ptr<cpp_builtin_type> build(std::string name)
+        static std::unique_ptr<cpp_builtin_type> build(std::string name)
         {
             return std::unique_ptr<cpp_builtin_type>(new cpp_builtin_type(std::move(name)));
         }
@@ -146,7 +146,7 @@ namespace cppast
     {
     public:
         /// \returns A newly created user-defined type.
-        std::unique_ptr<cpp_user_defined_type> build(cpp_type_ref entity)
+        static std::unique_ptr<cpp_user_defined_type> build(cpp_type_ref entity)
         {
             return std::unique_ptr<cpp_user_defined_type>(
                 new cpp_user_defined_type(std::move(entity)));
diff --git a/include/cppast/cpp_variable.hpp b/include/cppast/cpp_variable.hpp
index 2e75bc5..6e3663d 100644
--- a/include/cppast/cpp_variable.hpp
+++ b/include/cppast/cpp_variable.hpp
@@ -5,23 +5,11 @@
 #ifndef CPPAST_CPP_VARIABLE_HPP_INCLUDED
 #define CPPAST_CPP_VARIABLE_HPP_INCLUDED
 
+#include <cppast/cpp_storage_specifiers.hpp>
 #include <cppast/cpp_variable_base.hpp>
 
 namespace cppast
 {
-    /// Storage class and other specifiers for a [cppast::cpp_variable]().
-    enum cpp_variable_specifiers
-    {
-        cpp_var_none = 0,
-
-        cpp_var_static = 1,
-        cpp_var_extern = 2,
-
-        cpp_var_thread_local = 4,
-
-        cpp_var_constexpr = 8,
-    };
-
     /// A [cppast::cpp_entity]() modelling a C++ variable.
     /// \notes This is not a member variable,
     /// use [cppast::cpp_member_variable]() for that.
@@ -33,24 +21,34 @@ namespace cppast
         static std::unique_ptr<cpp_variable> build(const cpp_entity_index& idx, cpp_entity_id id,
                                                    std::string name, std::unique_ptr<cpp_type> type,
                                                    std::unique_ptr<cpp_expression> def,
-                                                   cpp_variable_specifiers         spec);
+                                                   cpp_storage_specifiers spec, bool is_constexpr);
 
-        /// \returns The [cppast::cpp_variable_specifiers]() on that variable.
-        cpp_variable_specifiers specifiers() const noexcept
+        /// \returns The [cppast::cpp_storage_specifiers]() on that variable.
+        cpp_storage_specifiers storage_class() const noexcept
         {
-            return specifiers_;
+            return storage_;
+        }
+
+        /// \returns Whether the variable is marked `constexpr`.
+        bool is_constexpr() const noexcept
+        {
+            return is_constexpr_;
         }
 
     private:
         cpp_variable(std::string name, std::unique_ptr<cpp_type> type,
-                     std::unique_ptr<cpp_expression> def, cpp_variable_specifiers spec)
-        : cpp_variable_base(std::move(name), std::move(type), std::move(def)), specifiers_(spec)
+                     std::unique_ptr<cpp_expression> def, cpp_storage_specifiers spec,
+                     bool is_constexpr)
+        : cpp_variable_base(std::move(name), std::move(type), std::move(def)),
+          storage_(spec),
+          is_constexpr_(is_constexpr)
         {
         }
 
         cpp_entity_kind do_get_entity_kind() const noexcept override;
 
-        cpp_variable_specifiers specifiers_;
+        cpp_storage_specifiers storage_;
+        bool                   is_constexpr_;
     };
 } // namespace cppast
 
diff --git a/src/cpp_entity_kind.cpp b/src/cpp_entity_kind.cpp
index 75bedb7..4d26f61 100644
--- a/src/cpp_entity_kind.cpp
+++ b/src/cpp_entity_kind.cpp
@@ -36,6 +36,11 @@ const char* cppast::to_string(cpp_entity_kind kind) noexcept
     case cpp_entity_kind::variable_t:
         return "variable";
 
+    case cpp_entity_kind::function_parameter_t:
+        return "function parameter";
+    case cpp_entity_kind::function_t:
+        return "function";
+
     case cpp_entity_kind::count:
         break;
     }
@@ -59,6 +64,8 @@ bool cppast::is_type(cpp_entity_kind kind) noexcept
     case cpp_entity_kind::using_declaration_t:
     case cpp_entity_kind::enum_value_t:
     case cpp_entity_kind::variable_t:
+    case cpp_entity_kind::function_parameter_t:
+    case cpp_entity_kind::function_t:
     case cpp_entity_kind::count:
         break;
     }
diff --git a/src/cpp_function.cpp b/src/cpp_function.cpp
new file mode 100644
index 0000000..54e4f5c
--- /dev/null
+++ b/src/cpp_function.cpp
@@ -0,0 +1,29 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#include <cppast/cpp_function.hpp>
+
+#include <cppast/cpp_entity_kind.hpp>
+
+using namespace cppast;
+
+std::unique_ptr<cpp_function_parameter> cpp_function_parameter::build(
+    const cpp_entity_index& idx, cpp_entity_id id, std::string name, std::unique_ptr<cpp_type> type,
+    std::unique_ptr<cpp_expression> def)
+{
+    auto result = std::unique_ptr<cpp_function_parameter>(
+        new cpp_function_parameter(std::move(name), std::move(type), std::move(def)));
+    idx.register_entity(std::move(id), type_safe::cref(*result));
+    return result;
+}
+
+cpp_entity_kind cpp_function_parameter::do_get_entity_kind() const noexcept
+{
+    return cpp_entity_kind::function_parameter_t;
+}
+
+cpp_entity_kind cpp_function::do_get_entity_kind() const noexcept
+{
+    return cpp_entity_kind::function_t;
+}
diff --git a/src/cpp_type.cpp b/src/cpp_type.cpp
index 93407df..0ddf58b 100644
--- a/src/cpp_type.cpp
+++ b/src/cpp_type.cpp
@@ -69,7 +69,7 @@ bool cppast::is_valid(const cpp_type& type) noexcept
         if (!can_compose(func.return_type()) || !is_valid(func.return_type()))
             return false;
 
-        for (auto& arg : func.argument_types())
+        for (auto& arg : func.parameter_types())
             if (!can_compose(arg) || !is_valid(arg))
                 return false;
 
@@ -84,7 +84,7 @@ bool cppast::is_valid(const cpp_type& type) noexcept
         else if (!can_compose(func.return_type()) || !is_valid(func.return_type()))
             return false;
 
-        for (auto& arg : func.argument_types())
+        for (auto& arg : func.parameter_types())
             if (!can_compose(arg) || !is_valid(arg))
                 return false;
 
diff --git a/src/cpp_variable.cpp b/src/cpp_variable.cpp
index bdec5fb..c084362 100644
--- a/src/cpp_variable.cpp
+++ b/src/cpp_variable.cpp
@@ -11,10 +11,10 @@ using namespace cppast;
 std::unique_ptr<cpp_variable> cpp_variable::build(const cpp_entity_index& idx, cpp_entity_id id,
                                                   std::string name, std::unique_ptr<cpp_type> type,
                                                   std::unique_ptr<cpp_expression> def,
-                                                  cpp_variable_specifiers         spec)
+                                                  cpp_storage_specifiers spec, bool is_constexpr)
 {
     auto result = std::unique_ptr<cpp_variable>(
-        new cpp_variable(std::move(name), std::move(type), std::move(def), spec));
+        new cpp_variable(std::move(name), std::move(type), std::move(def), spec, is_constexpr));
     idx.register_entity(std::move(id), type_safe::cref(*result));
     return result;
 }
diff --git a/src/visitor.cpp b/src/visitor.cpp
index 9f65191..951ae18 100644
--- a/src/visitor.cpp
+++ b/src/visitor.cpp
@@ -8,6 +8,7 @@
 #include <cppast/cpp_entity_kind.hpp>
 #include <cppast/cpp_enum.hpp>
 #include <cppast/cpp_file.hpp>
+#include <cppast/cpp_function.hpp>
 #include <cppast/cpp_language_linkage.hpp>
 #include <cppast/cpp_namespace.hpp>
 
@@ -44,6 +45,8 @@ bool detail::visit(const cpp_entity& e, detail::visitor_callback_t cb, void* fun
         return handle_container<cpp_namespace>(e, cb, functor);
     case cpp_entity_kind::enum_t:
         return handle_container<cpp_enum>(e, cb, functor);
+    case cpp_entity_kind::function_t:
+        return handle_container<cpp_function>(e, cb, functor);
 
     case cpp_entity_kind::namespace_alias_t:
     case cpp_entity_kind::using_directive_t:
@@ -51,6 +54,7 @@ bool detail::visit(const cpp_entity& e, detail::visitor_callback_t cb, void* fun
     case cpp_entity_kind::type_alias_t:
     case cpp_entity_kind::enum_value_t:
     case cpp_entity_kind::variable_t:
+    case cpp_entity_kind::function_parameter_t:
         return cb(functor, e, visitor_info::leaf_entity);
 
     case cpp_entity_kind::count: