diff --git a/trixy-parser/docs/grammar.ebnf b/trixy-parser/docs/grammar.ebnf
index 2e6c098..9435ee9 100644
--- a/trixy-parser/docs/grammar.ebnf
+++ b/trixy-parser/docs/grammar.ebnf
@@ -35,7 +35,7 @@ Namespace = {DocComment} {Attribute} "mod" Identifier "{" {Function | Namespace
 Structure = {DocComment} {Attribute} "struct" Identifier "{"  [DocNamedType {"," DocNamedType } [","]] "}";
 Enumeration = {DocComment} {Attribute} "enum" Identifier "{"  [DocIdentifier {"," DocIdentifier} [","]] "}";
 
-Type = Identifier ["<" Type {"," Type} ">"];
+Type = Identifier ["<" Type {"," Type} ">"] | "fn" "(" [NamedType {"," NamedType }] ")" [ "->" Type ];
 StringLiteral = ["r"] "\"" {ANYTHING} "\"" | "r" "#" {"#"} "\"" {ANYTHING} "#" {"#"} "\"";
 
 Identifier = (CHARACTER | "_") { NUMBER | CHARACTER | "_" } ;
diff --git a/trixy-parser/src/command_spec/checked.rs b/trixy-parser/src/command_spec/checked.rs
index 23625ce..078e5dc 100644
--- a/trixy-parser/src/command_spec/checked.rs
+++ b/trixy-parser/src/command_spec/checked.rs
@@ -25,7 +25,7 @@ use std::fmt::{Display, Write};
 
 use crate::lexing::TokenKind;
 
-use super::unchecked;
+use super::unchecked::{self, DeriveValue};
 
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
 pub enum Variant {
@@ -103,34 +103,95 @@ pub struct Function {
 }
 
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
-pub struct Type {
-    pub identifier: Identifier,
-    pub generic_args: Vec<Type>,
+pub enum Type {
+    Typical {
+        identifier: Identifier,
+        generic_args: Vec<Type>,
+    },
+    Function {
+        inputs: Vec<NamedType>,
+        output: Option<Box<Type>>,
+    },
 }
-impl Display for Type {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let ident = &self.identifier.name;
 
-        f.write_str(ident)?;
-        if !self.generic_args.is_empty() {
-            f.write_char('<')?;
-            let mut first_run = true;
-            for arg in &self.generic_args {
-                if !first_run {
-                    f.write_str(", ")?;
+impl Type {
+    pub fn print_generics(&self) -> String {
+        let mut output = String::new();
+        self.display_generics(&mut output)
+            .expect("This should fail");
+        output
+    }
+    pub fn display_generics<T: Write>(&self, f: &mut T) -> std::fmt::Result {
+        match self {
+            Type::Typical {
+                identifier: _,
+                generic_args,
+            } => {
+                if !generic_args.is_empty() {
+                    f.write_char('<')?;
+                    let mut first_run = true;
+                    for arg in generic_args {
+                        if !first_run {
+                            f.write_str(", ")?;
+                        } else {
+                            first_run = false;
+                        }
+                        write!(f, "{}", arg)?;
+                    }
+                    f.write_char('>')
                 } else {
-                    first_run = false;
+                    f.write_str("")
                 }
-                write!(f, "{}", arg)?;
             }
-            f.write_char('>')
-        } else {
-            f.write_str("")
+            Type::Function { .. } => {
+                unimplemented!("This function should only be called for the 'Typical' enum variant")
+            }
         }
     }
 }
 
-#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
+impl Display for Type {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Type::Typical {
+                identifier,
+                generic_args: _,
+            } => {
+                f.write_str(&identifier.name)?;
+                self.display_generics(f)
+            }
+            Type::Function { inputs, output } => {
+                f.write_str("fn(")?;
+                if !inputs.is_empty() {
+                    f.write_str(
+                        &inputs
+                            .iter()
+                            .map(|ty| ty.to_string())
+                            .collect::<Vec<_>>()
+                            .join(", "),
+                    )?;
+                }
+
+                f.write_str(")")?;
+                if let Some(output) = output {
+                    f.write_str("-> ")?;
+                    f.write_str(output.to_string().as_str())?;
+                }
+                Ok(())
+            }
+        }
+    }
+}
+
+impl Display for NamedType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.name.name)?;
+        f.write_str(": ")?;
+        f.write_str(self.r#type.to_string().as_str())
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
 pub struct NamedType {
     pub name: Identifier,
     pub r#type: Type,
diff --git a/trixy-parser/src/command_spec/unchecked.rs b/trixy-parser/src/command_spec/unchecked.rs
index 7712b87..648a670 100644
--- a/trixy-parser/src/command_spec/unchecked.rs
+++ b/trixy-parser/src/command_spec/unchecked.rs
@@ -25,7 +25,7 @@
 
 use std::fmt::{Display, Write};
 
-use crate::lexing::{Token, TokenSpan};
+use crate::lexing::{Token, TokenKind, TokenSpan};
 
 #[derive(Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
 pub struct CommandSpec {
@@ -173,33 +173,77 @@ pub struct NamedType {
 }
 
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
-pub struct Type {
-    pub identifier: Token, // Will later become an Identifier
-    pub generic_args: Vec<Type>,
+pub enum Type {
+    Typical {
+        identifier: Token, // Will later become an Identifier
+        generic_args: Vec<Type>,
+    },
+    Function {
+        inputs: Vec<NamedType>,
+        output: Option<Box<Type>>,
+    },
+}
+
+impl Display for NamedType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let ident = match self.name.kind() {
+               crate::lexing::TokenKind::Identifier(ident) => ident,
+               _ => panic!("Tried to display a non identifier token in the Type display implementation. This is a bug"),
+           };
+        f.write_str(ident)?;
+        f.write_str(": ")?;
+        f.write_str(self.r#type.to_string().as_str())
+    }
 }
 
 impl Display for Type {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let ident = match self.identifier.kind() {
-            crate::lexing::TokenKind::Identifier(ident) => ident,
-            _ => panic!("Tried to display a non identifier token in the Type display implementation. This is a bug"),
-        };
+        match self {
+            Type::Typical {
+                identifier,
+                generic_args,
+            } => {
+                let ident = match identifier.kind() {
+                    crate::lexing::TokenKind::Identifier(ident) => ident,
+                    _ => panic!("Tried to display a non identifier token in the Type display implementation. This is a bug"),
+                };
 
-        f.write_str(ident)?;
-        if !self.generic_args.is_empty() {
-            f.write_char('<')?;
-            let mut first_run = true;
-            for arg in &self.generic_args {
-                if !first_run {
-                    f.write_str(", ")?;
+                f.write_str(ident)?;
+                if !generic_args.is_empty() {
+                    f.write_char('<')?;
+                    let mut first_run = true;
+                    for arg in generic_args {
+                        if !first_run {
+                            f.write_str(", ")?;
+                        } else {
+                            first_run = false;
+                        }
+                        write!(f, "{}", arg)?;
+                    }
+                    f.write_char('>')
                 } else {
-                    first_run = false;
+                    f.write_str("")
                 }
-                write!(f, "{}", arg)?;
             }
-            f.write_char('>')
-        } else {
-            f.write_str("")
+            Type::Function { inputs, output } => {
+                f.write_str("fn(")?;
+                if !inputs.is_empty() {
+                    f.write_str(
+                        &inputs
+                            .iter()
+                            .map(|ty| ty.to_string())
+                            .collect::<Vec<_>>()
+                            .join(", "),
+                    )?;
+                }
+
+                f.write_str(")")?;
+                if let Some(output) = output {
+                    f.write_str("-> ")?;
+                    f.write_str(output.to_string().as_str())?;
+                }
+                Ok(())
+            }
         }
     }
 }
diff --git a/trixy-parser/src/parsing/checked/mod.rs b/trixy-parser/src/parsing/checked/mod.rs
index 9a3163c..8f35790 100644
--- a/trixy-parser/src/parsing/checked/mod.rs
+++ b/trixy-parser/src/parsing/checked/mod.rs
@@ -286,25 +286,101 @@ impl Parser {
         })
     }
 
-    fn process_type(&mut self, mut r#type: UncheckedType) -> Result<Type, ParsingError> {
-        let identifier: Identifier =
-            mem::take(&mut r#type.identifier.kind).to_identifier(Variant::Void);
+    fn process_type(&mut self, r#type: UncheckedType) -> Result<Type, ParsingError> {
+        match r#type {
+            UncheckedType::Typical {
+                identifier,
+                generic_args,
+            } => self.process_typical_type(identifier, generic_args),
+            UncheckedType::Function { inputs, output } => {
+                self.process_function_type(inputs, output)
+            }
+        }
+    }
 
+    fn process_typical_type(
+        &mut self,
+        mut type_identifier: Token,
+        generic_args: Vec<UncheckedType>,
+    ) -> Result<Type, ParsingError> {
+        fn match_to_vector_struct(matches: Vec<&UncheckedStructure>) -> Vec<Identifier> {
+            matches
+                .first()
+                .expect("This exists")
+                .namespaces
+                .iter()
+                .map(|token| match token.kind() {
+                    TokenKind::Identifier(ident) => Identifier {
+                        name: ident.to_owned(),
+                        variant: Variant::Namespace,
+                    },
+                    _ => unreachable!("This should not be here"),
+                })
+                .collect()
+        }
+        fn match_to_vector_enum(matches: Vec<&UncheckedEnumeration>) -> Vec<Identifier> {
+            matches
+                .first()
+                .expect("This exists")
+                .namespaces
+                .iter()
+                .map(|token| match token.kind() {
+                    TokenKind::Identifier(ident) => Identifier {
+                        name: ident.to_owned(),
+                        variant: Variant::Namespace,
+                    },
+                    _ => unreachable!("This should not be here"),
+                })
+                .collect()
+        }
+
+        let identifier: Identifier =
+            mem::take(&mut type_identifier.kind).to_identifier(Variant::Void);
         let variant: Variant;
-        if self
+
+        let matched_structures: Vec<_> = self
             .structures
             .iter()
-            .map(|r#struct| (r#struct.identifier.kind.clone()).to_identifier(Variant::Void))
-            .any(|ident| ident == identifier)
-        {
-            variant = Variant::Structure;
-        } else if self
+            .filter(|r#struct| {
+                (r#struct.identifier.kind.clone()).to_identifier(Variant::Void) == identifier
+            })
+            .collect();
+        let matched_enumerations: Vec<_> = self
             .enumerations
             .iter()
-            .map(|r#enum| (r#enum.identifier.kind.clone()).to_identifier(Variant::Void))
-            .any(|ident| ident == identifier)
-        {
-            variant = Variant::Enumeration;
+            .filter(|r#enum| {
+                (r#enum.identifier.kind.clone()).to_identifier(Variant::Void) == identifier
+            })
+            .collect();
+
+        if !matched_structures.is_empty() {
+            if matched_structures.len() != 1 {
+                return Err(error::ParsingError::StructureCopied {
+                    structure: identifier,
+                    span: *matched_structures
+                        .first()
+                        .expect("Exists")
+                        .identifier
+                        .span(),
+                });
+            }
+            variant = Variant::Structure {
+                namespace: match_to_vector_struct(matched_structures),
+            };
+        } else if !matched_enumerations.is_empty() {
+            if matched_enumerations.len() != 1 {
+                return Err(error::ParsingError::EnumerationCopied {
+                    enumeration: identifier,
+                    span: *matched_enumerations
+                        .first()
+                        .expect("Exists")
+                        .identifier
+                        .span(),
+                });
+            }
+            variant = Variant::Enumeration {
+                namespace: match_to_vector_enum(matched_enumerations),
+            };
         } else if BASE_TYPES
             .iter()
             .any(|(ident, _)| ident == &identifier.name)
@@ -313,7 +389,7 @@ impl Parser {
         } else {
             return Err(ParsingError::TypeNotDeclared {
                 r#type: identifier,
-                span: r#type.identifier.span,
+                span: type_identifier.span,
             });
         }
         let identifier: Identifier = Identifier {
@@ -338,43 +414,63 @@ impl Parser {
 
                 if !fitting_types
                     .iter()
-                    .any(|generic_number| *generic_number == &r#type.generic_args.len())
+                    .any(|generic_number| *generic_number == &generic_args.len())
                 {
-                    if r#type.generic_args.len() < **min_fitting_type {
+                    if generic_args.len() < **min_fitting_type {
                         return Err(ParsingError::NotEnoughGenericArgs {
                             expected_min: **min_fitting_type,
-                            got: r#type.generic_args.len(),
+                            got: generic_args.len(),
                             r#type: identifier,
-                            span: r#type.identifier.span,
+                            span: type_identifier.span,
                         });
-                    } else if r#type.generic_args.len() > **max_fitting_type {
+                    } else if generic_args.len() > **max_fitting_type {
                         return Err(ParsingError::TooManyGenericArgs {
                             expected_max: **max_fitting_type,
-                            got: r#type.generic_args.len(),
+                            got: generic_args.len(),
                             r#type: identifier,
-                            span: r#type.identifier.span,
+                            span: type_identifier.span,
                         });
                     }
                 }
-            } else if fitting_types.is_empty() && !r#type.generic_args.is_empty() {
+            } else if fitting_types.is_empty() && !generic_args.is_empty() {
                 // Self declared types can not have generic arguments
                 return Err(ParsingError::TooManyGenericArgs {
                     expected_max: 0,
-                    got: r#type.generic_args.len(),
+                    got: generic_args.len(),
                     r#type: identifier,
-                    span: r#type.identifier.span,
+                    span: type_identifier.span,
                 });
             }
         }
 
-        let mut generic_args = vec![];
-        for generic_arg in r#type.generic_args {
-            generic_args.push(self.process_type(generic_arg)?);
+        let mut new_generic_args: Vec<checked::Type> = vec![];
+        for generic_arg in generic_args {
+            new_generic_args.push(self.process_type(generic_arg)?);
         }
 
-        Ok(Type {
+        Ok(Type::Typical {
             identifier,
-            generic_args,
+            generic_args: new_generic_args,
+        })
+    }
+    fn process_function_type(
+        &mut self,
+        inputs: Vec<UncheckedNamedType>,
+        output: Option<Box<UncheckedType>>,
+    ) -> Result<Type, ParsingError> {
+        let inputs = inputs
+            .into_iter()
+            .map(|input| self.process_named_type(input))
+            .collect::<Result<Vec<NamedType>, ParsingError>>()?;
+
+        let mut new_output = None;
+        if let Some(output) = output {
+            new_output = Some(Box::new(self.process_type(*output)?));
+        }
+
+        Ok(Type::Function {
+            inputs,
+            output: new_output,
         })
     }
 }
diff --git a/trixy-parser/src/parsing/unchecked/mod.rs b/trixy-parser/src/parsing/unchecked/mod.rs
index a244fae..43dcb7d 100644
--- a/trixy-parser/src/parsing/unchecked/mod.rs
+++ b/trixy-parser/src/parsing/unchecked/mod.rs
@@ -122,24 +122,51 @@ impl Parser {
     }
 
     fn parse_type(&mut self) -> Result<Type, ParsingError> {
-        let identifier = self.expect(token![Ident])?;
+        if self.expect_peek(token![Ident]) {
+            let identifier = self.expect(token![Ident])?;
+
+            let mut generic_args = vec![];
+            if self.expect_peek(token![<]) {
+                self.expect(token![<])?;
+                if self.expect_peek(token![Ident]) {
+                    generic_args.push(self.parse_type()?);
+                }
+                while self.expect_peek(token![Comma]) {
+                    self.expect(token![Comma])?;
+                    generic_args.push(self.parse_type()?);
+                }
+                self.expect(token![>])?;
+            }
+            Ok(Type::Typical {
+                identifier,
+                generic_args,
+            })
+        } else {
+            // we got a function type
+            self.expect(token![fn])?;
+            self.expect(token![CurvedBracketOpen])?;
+            let mut inputs = vec![];
 
-        let mut generic_args = vec![];
-        if self.expect_peek(token![<]) {
-            self.expect(token![<])?;
             if self.expect_peek(token![Ident]) {
-                generic_args.push(self.parse_type()?);
+                inputs.push(self.parse_named_type()?);
             }
             while self.expect_peek(token![Comma]) {
                 self.expect(token![Comma])?;
-                generic_args.push(self.parse_type()?);
+                inputs.push(self.parse_named_type()?);
             }
-            self.expect(token![>])?;
+
+            self.expect(token![CurvedBracketClose])?;
+            let mut output_type = None;
+            if self.expect_peek(token![->]) {
+                self.expect(token![->])?;
+                output_type = Some(Box::new(self.parse_type()?));
+            }
+
+            Ok(Type::Function {
+                inputs,
+                output: output_type,
+            })
         }
-        Ok(Type {
-            identifier,
-            generic_args,
-        })
     }
 
     fn parse_bracket_string_literal(&mut self) -> Result<StringLiteral, ParsingError> {