diff --git a/src/abstract_tree/enum_defintion.rs b/src/abstract_tree/enum_defintion.rs
index 2301d00..c44e6a0 100644
--- a/src/abstract_tree/enum_defintion.rs
+++ b/src/abstract_tree/enum_defintion.rs
@@ -3,32 +3,89 @@ use tree_sitter::Node as SyntaxNode;
 
 use crate::{
     error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Type, Value,
+    AbstractTree, Context, EnumInstance, Format, Identifier, Type, TypeDefinition, Value,
 };
 
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct EnumDefinition;
+pub struct EnumDefinition {
+    identifier: Identifier,
+    variants: Vec<(Identifier, VariantContent)>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
+enum VariantContent {
+    Type(Type),
+    TypeDefinition(TypeDefinition),
+    None,
+}
+
+impl EnumDefinition {
+    pub fn instantiate(&self, variant: String, content: Value) -> EnumInstance {
+        EnumInstance::new(self.identifier.inner().clone(), variant, content)
+    }
+}
 
 impl AbstractTree for EnumDefinition {
     fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        todo!()
+        SyntaxError::expect_syntax_node(source, "enum_definition", node)?;
+
+        let identifier_node = node.child(1).unwrap();
+        let identifier = Identifier::from_syntax(identifier_node, source, context)?;
+
+        let mut variants = Vec::new();
+        let mut current_identifier = None;
+
+        for index in 3..node.child_count() - 1 {
+            let child = node.child(index).unwrap();
+
+            if child.kind() == "identifier" {
+                current_identifier = Some(Identifier::from_syntax(child, source, context)?);
+            }
+
+            if let Some(identifier) = &current_identifier {
+                if child.kind() == "type" {
+                    let r#type = Type::from_syntax(child, source, context)?;
+
+                    variants.push((identifier.clone(), VariantContent::Type(r#type)));
+                }
+
+                if child.kind() == "type_definition" {
+                    let type_definition = TypeDefinition::from_syntax(child, source, context)?;
+
+                    variants.push((
+                        identifier.clone(),
+                        VariantContent::TypeDefinition(type_definition),
+                    ));
+                }
+            }
+        }
+
+        Ok(EnumDefinition {
+            identifier,
+            variants,
+        })
     }
 
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        todo!()
+    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
+        Ok(Type::None)
     }
 
-    fn validate(&self, source: &str, context: &Context) -> Result<(), ValidationError> {
-        todo!()
+    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
+        Ok(())
     }
 
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        todo!()
+    fn run(&self, _source: &str, context: &Context) -> Result<Value, RuntimeError> {
+        context.set_definition(
+            self.identifier.inner().clone(),
+            TypeDefinition::Enum(self.clone()),
+        )?;
+
+        Ok(Value::none())
     }
 }
 
 impl Format for EnumDefinition {
-    fn format(&self, output: &mut String, indent_level: u8) {
+    fn format(&self, _output: &mut String, _indent_level: u8) {
         todo!()
     }
 }
diff --git a/src/abstract_tree/statement.rs b/src/abstract_tree/statement.rs
index b993c9b..fbec2f6 100644
--- a/src/abstract_tree/statement.rs
+++ b/src/abstract_tree/statement.rs
@@ -57,9 +57,12 @@ impl AbstractTree for Statement {
 
                 Ok(Statement::Return(Box::new(Statement::from_syntax(statement_node, source, context)?)))
             },
+            "type_definition" => Ok(Statement::TypeDefinition(TypeDefinition::from_syntax(
+                child, source, context
+            )?)),
             _ => Err(SyntaxError::UnexpectedSyntaxNode {
                 expected:
-                    "assignment, index assignment, expression, block, return, if...else, while, for or match".to_string(),
+                    "assignment, index assignment, expression, type_definition, block, return, if...else, while, for or match".to_string(),
                 actual: child.kind().to_string(),
                 location: child.start_position(),
                 relevant_source: source[child.byte_range()].to_string(),
diff --git a/src/abstract_tree/type_definition.rs b/src/abstract_tree/type_definition.rs
index b050704..41f7446 100644
--- a/src/abstract_tree/type_definition.rs
+++ b/src/abstract_tree/type_definition.rs
@@ -34,21 +34,32 @@ impl AbstractTree for TypeDefinition {
         }
     }
 
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        todo!()
+    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
+        match self {
+            TypeDefinition::Enum(enum_definition) => enum_definition.expected_type(_context),
+            TypeDefinition::Struct(struct_definition) => struct_definition.expected_type(_context),
+        }
     }
 
-    fn validate(&self, source: &str, context: &Context) -> Result<(), ValidationError> {
-        todo!()
+    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
+        match self {
+            TypeDefinition::Enum(enum_definition) => enum_definition.validate(_source, _context),
+            TypeDefinition::Struct(struct_definition) => {
+                struct_definition.validate(_source, _context)
+            }
+        }
     }
 
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        todo!()
+    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
+        match self {
+            TypeDefinition::Enum(enum_definition) => enum_definition.run(_source, _context),
+            TypeDefinition::Struct(struct_definition) => struct_definition.run(_source, _context),
+        }
     }
 }
 
 impl Format for TypeDefinition {
-    fn format(&self, output: &mut String, indent_level: u8) {
+    fn format(&self, _output: &mut String, _indent_level: u8) {
         todo!()
     }
 }
diff --git a/src/abstract_tree/value_node.rs b/src/abstract_tree/value_node.rs
index 1a15b9d..4539877 100644
--- a/src/abstract_tree/value_node.rs
+++ b/src/abstract_tree/value_node.rs
@@ -1,11 +1,13 @@
 use std::{cmp::Ordering, collections::BTreeMap, ops::RangeInclusive};
 
 use serde::{Deserialize, Serialize};
+use tree_sitter::Node as SyntaxNode;
 
 use crate::{
     error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, BuiltInValue, Context, Expression, Format, Function, FunctionNode, Identifier,
-    List, Map, SourcePosition, Statement, Structure, SyntaxNode, Type, TypeSpecification, Value,
+    AbstractTree, BuiltInValue, Context, Expression, Format, Function, FunctionNode,
+    Identifier, List, Map, SourcePosition, Statement, Structure, Type,
+    TypeSpecification, Value, TypeDefinition,
 };
 
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq)]
@@ -19,8 +21,13 @@ pub enum ValueNode {
     Option(Option<Box<Expression>>),
     Map(BTreeMap<String, (Statement, Option<Type>)>, SourcePosition),
     BuiltInValue(BuiltInValue),
-    Structure(BTreeMap<String, (Option<Statement>, Type)>),
     Range(RangeInclusive<i64>),
+    Structure(BTreeMap<String, (Option<Statement>, Type)>),
+    Enum {
+        name: Identifier,
+        variant: Identifier,
+        expression: Option<Box<Expression>>,
+    },
 }
 
 impl AbstractTree for ValueNode {
@@ -167,10 +174,25 @@ impl AbstractTree for ValueNode {
 
                 ValueNode::Range(start..=end)
             }
+            "enum_instance" => {
+                let name_node = child.child(1).unwrap();
+                let name = Identifier::from_syntax(name_node, source, context)?;
+                
+                let variant_node = child.child(3).unwrap();
+                let variant = Identifier::from_syntax(variant_node, source, context)?;
+             
+                let expression = if let Some(expression_node) = child.child(5) {                
+                    Some(Box::new(Expression::from_syntax(expression_node, source, context)?))
+                } else {
+                    None
+                };
+
+                ValueNode::Enum { name, variant , expression  }                
+            }
             _ => {
                 return Err(SyntaxError::UnexpectedSyntaxNode {
                     expected:
-                        "string, integer, float, boolean, range, list, map, option, function or structure"
+                        "string, integer, float, boolean, range, list, map, option, function, structure or enum"
                             .to_string(),
                     actual: child.kind().to_string(),
                     location: child.start_position(),
@@ -229,6 +251,7 @@ impl AbstractTree for ValueNode {
                 Type::Map(Some(Structure::new(value_map)))
             }
             ValueNode::Range(_) => Type::Range,
+            ValueNode::Enum { name, .. } => Type::Custom(name.clone()),
         };
 
         Ok(r#type)
@@ -256,7 +279,7 @@ impl AbstractTree for ValueNode {
                     }
                 }
             }
-            _ => {}
+            _ => {},
         }
 
         Ok(())
@@ -323,6 +346,30 @@ impl AbstractTree for ValueNode {
                 Value::Structure(Structure::new(value_map))
             }
             ValueNode::Range(range) => Value::Range(range.clone()),
+            ValueNode::Enum { name, variant, expression } => {
+                let value = if let Some(expression) = expression {
+                    expression.run(source, context)?
+                } else {
+                    Value::none()
+                };
+                let instance = if let Some(definition) = context.get_definition(name.inner())? {
+                    if let TypeDefinition::Enum(enum_defintion) = definition {
+                        enum_defintion.instantiate(variant.inner().clone(), value)
+                    } else {
+                        return Err(RuntimeError::ValidationFailure(
+                            ValidationError::ExpectedEnumDefintion {
+                                actual: definition.clone()
+                            }
+                        ));
+                    }
+                } else {
+                    return Err(RuntimeError::ValidationFailure(
+                        ValidationError::TypeDefinitionNotFound(name.inner().clone())
+                    ));
+                };
+
+                Value::Enum(instance)                
+            },
         };
 
         Ok(value)
@@ -407,6 +454,7 @@ impl Format for ValueNode {
                 output.push('}');
             }
             ValueNode::Range(_) => todo!(),
+            ValueNode::Enum { ..  } => todo!(),
         }
     }
 }
@@ -434,6 +482,29 @@ impl Ord for ValueNode {
             (ValueNode::BuiltInValue(_), _) => Ordering::Greater,
             (ValueNode::Structure(left), ValueNode::Structure(right)) => left.cmp(right),
             (ValueNode::Structure(_), _) => Ordering::Greater,
+            (
+                ValueNode::Enum {
+                    name: left_name, variant: left_variant, expression: left_expression
+                },
+                ValueNode::Enum {
+                    name: right_name, variant: right_variant, expression: right_expression
+                }
+            ) => {
+                let name_cmp = left_name.cmp(right_name);
+
+                if name_cmp.is_eq() {
+                    let variant_cmp = left_variant.cmp(right_variant);
+
+                    if variant_cmp.is_eq() {
+                        left_expression.cmp(right_expression)
+                    } else {
+                        variant_cmp
+                    }
+                } else {
+                    name_cmp
+                }
+            },
+            (ValueNode::Enum { .. }, _) => Ordering::Greater,
             (ValueNode::Range(left), ValueNode::Range(right)) => left.clone().cmp(right.clone()),
             (ValueNode::Range(_), _) => Ordering::Less,
         }
diff --git a/src/context.rs b/src/context.rs
index 7c362e6..443a814 100644
--- a/src/context.rs
+++ b/src/context.rs
@@ -4,7 +4,7 @@ use std::{
     sync::{Arc, RwLock, RwLockReadGuard},
 };
 
-use crate::{error::rw_lock_error::RwLockError, Type, Value};
+use crate::{error::rw_lock_error::RwLockError, Type, TypeDefinition, Value};
 
 #[derive(Clone, Debug)]
 pub struct Context {
@@ -65,12 +65,23 @@ impl Context {
             match value_data {
                 ValueData::Value { inner, .. } => Ok(Some(inner.r#type())),
                 ValueData::ExpectedType { inner, .. } => Ok(Some(inner.clone())),
+                ValueData::TypeDefinition(_) => todo!(),
             }
         } else {
             Ok(None)
         }
     }
 
+    pub fn get_definition(&self, key: &str) -> Result<Option<TypeDefinition>, RwLockError> {
+        if let Some(value_data) = self.inner.read()?.get(key) {
+            if let ValueData::TypeDefinition(definition) = value_data {
+                return Ok(Some(definition.clone()));
+            }
+        }
+
+        Ok(None)
+    }
+
     pub fn set_value(&self, key: String, value: Value) -> Result<(), RwLockError> {
         self.inner.write()?.insert(
             key,
@@ -91,6 +102,18 @@ impl Context {
         Ok(())
     }
 
+    pub fn set_definition(
+        &self,
+        key: String,
+        definition: TypeDefinition,
+    ) -> Result<(), RwLockError> {
+        self.inner
+            .write()?
+            .insert(key, ValueData::TypeDefinition(definition));
+
+        Ok(())
+    }
+
     pub fn unset(&self, key: &str) -> Result<(), RwLockError> {
         self.inner.write()?.remove(key);
 
@@ -151,6 +174,7 @@ pub enum ValueData {
     ExpectedType {
         inner: Type,
     },
+    TypeDefinition(TypeDefinition),
 }
 
 impl Eq for ValueData {}
@@ -207,6 +231,8 @@ impl Ord for ValueData {
                 ValueData::ExpectedType { inner: inner_left },
                 ValueData::ExpectedType { inner: inner_right },
             ) => inner_left.cmp(inner_right),
+            (ValueData::TypeDefinition(left), ValueData::TypeDefinition(right)) => left.cmp(right),
+            (ValueData::TypeDefinition(_), _) => Greater,
             (ValueData::ExpectedType { .. }, _) => Less,
         }
     }
diff --git a/src/error/runtime_error.rs b/src/error/runtime_error.rs
index 94ff109..8c6821d 100644
--- a/src/error/runtime_error.rs
+++ b/src/error/runtime_error.rs
@@ -9,7 +9,7 @@ use std::{
 
 use crate::{Type, Value};
 
-use super::rw_lock_error::RwLockError;
+use super::{rw_lock_error::RwLockError, ValidationError};
 
 #[derive(Debug, PartialEq)]
 pub enum RuntimeError {
@@ -114,6 +114,8 @@ pub enum RuntimeError {
         expected: usize,
         actual: usize,
     },
+
+    ValidationFailure(ValidationError),
 }
 
 impl RuntimeError {
diff --git a/src/error/validation_error.rs b/src/error/validation_error.rs
index efea76a..133ca0c 100644
--- a/src/error/validation_error.rs
+++ b/src/error/validation_error.rs
@@ -2,7 +2,7 @@ use std::fmt::{self, Display, Formatter};
 
 use serde::{Deserialize, Serialize};
 
-use crate::{Identifier, SourcePosition, Type, Value};
+use crate::{Identifier, SourcePosition, Type, TypeDefinition, Value};
 
 use super::rw_lock_error::RwLockError;
 
@@ -61,8 +61,14 @@ pub enum ValidationError {
         position: SourcePosition,
     },
 
-    /// Failed to find a variable with a value for this key.
+    /// Failed to find a value with this key.
     VariableIdentifierNotFound(Identifier),
+
+    /// Failed to find a type definition with this key.
+    TypeDefinitionNotFound(String),
+
+    /// Failed to find a type definition with this key.
+    ExpectedEnumDefintion { actual: TypeDefinition },
 }
 
 impl ValidationError {
diff --git a/src/main.rs b/src/main.rs
index e5c20ae..f9069b6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -310,6 +310,7 @@ impl Completer for DustCompleter {
             let value = match value_data {
                 ValueData::Value { inner, .. } => inner,
                 ValueData::ExpectedType { .. } => continue,
+                ValueData::TypeDefinition(_) => continue,
             };
 
             if key.contains(last_word) {
diff --git a/src/value/enum.rs b/src/value/enum.rs
index 556780a..c9bfa46 100644
--- a/src/value/enum.rs
+++ b/src/value/enum.rs
@@ -1,14 +1,16 @@
-use crate::{Identifier, Value};
+use crate::Value;
 
-#[derive(Debug, Clone)]
-pub struct Enum {
+#[derive(Debug, Clone, Eq, PartialEq, PartialOrd, Ord)]
+pub struct EnumInstance {
+    name: String,
     variant_name: String,
     value: Box<Value>,
 }
 
-impl Enum {
-    pub fn new(variant_name: String, value: Value) -> Self {
+impl EnumInstance {
+    pub fn new(name: String, variant_name: String, value: Value) -> Self {
         Self {
+            name,
             variant_name,
             value: Box::new(value),
         }
diff --git a/src/value/mod.rs b/src/value/mod.rs
index b3085f0..c7931ba 100644
--- a/src/value/mod.rs
+++ b/src/value/mod.rs
@@ -16,7 +16,9 @@ use std::{
     ops::{Add, AddAssign, Div, Mul, RangeInclusive, Rem, Sub, SubAssign},
 };
 
-pub use self::{function::Function, list::List, map::Map, r#enum::Enum, structure::Structure};
+pub use self::{
+    function::Function, list::List, map::Map, r#enum::EnumInstance, structure::Structure,
+};
 
 pub mod r#enum;
 pub mod function;
@@ -41,7 +43,7 @@ pub enum Value {
     Range(RangeInclusive<i64>),
     Option(Option<Box<Value>>),
     Structure(Structure),
-    Enum(Enum),
+    Enum(EnumInstance),
 }
 
 impl Default for Value {
@@ -443,8 +445,9 @@ impl PartialEq for Value {
             (Value::Map(left), Value::Map(right)) => left == right,
             (Value::Function(left), Value::Function(right)) => left == right,
             (Value::Option(left), Value::Option(right)) => left == right,
-            (Value::Structure(left), Value::Structure(right)) => left == right,
             (Value::Range(left), Value::Range(right)) => left == right,
+            (Value::Structure(left), Value::Structure(right)) => left == right,
+            (Value::Enum(left), Value::Enum(right)) => left == right,
             _ => false,
         }
     }
@@ -483,6 +486,8 @@ impl Ord for Value {
             (Value::Function(_), _) => Ordering::Greater,
             (Value::Structure(left), Value::Structure(right)) => left.cmp(right),
             (Value::Structure(_), _) => Ordering::Greater,
+            (Value::Enum(left), Value::Enum(right)) => left.cmp(right),
+            (Value::Enum(_), _) => Ordering::Greater,
             (Value::Range(left), Value::Range(right)) => {
                 let left_len = left.end() - left.start();
                 let right_len = right.end() - right.start();
@@ -492,17 +497,6 @@ impl Ord for Value {
             (Value::Range(_), _) => Ordering::Greater,
             (Value::Option(left), Value::Option(right)) => left.cmp(right),
             (Value::Option(_), _) => Ordering::Less,
-            (Value::Enum(_), Value::List(_)) => todo!(),
-            (Value::Enum(_), Value::Map(_)) => todo!(),
-            (Value::Enum(_), Value::Function(_)) => todo!(),
-            (Value::Enum(_), Value::String(_)) => todo!(),
-            (Value::Enum(_), Value::Float(_)) => todo!(),
-            (Value::Enum(_), Value::Integer(_)) => todo!(),
-            (Value::Enum(_), Value::Boolean(_)) => todo!(),
-            (Value::Enum(_), Value::Range(_)) => todo!(),
-            (Value::Enum(_), Value::Option(_)) => todo!(),
-            (Value::Enum(_), Value::Structure(_)) => todo!(),
-            (Value::Enum(_), Value::Enum(_)) => todo!(),
         }
     }
 }
diff --git a/tests/enums.rs b/tests/enums.rs
index b18b5b6..046c1a1 100644
--- a/tests/enums.rs
+++ b/tests/enums.rs
@@ -15,6 +15,10 @@ fn simple_enum() {
 
     assert_eq!(
         result,
-        Ok(Value::Enum(Enum::new("Foo".to_string(), Value::none())))
+        Ok(Value::Enum(EnumInstance::new(
+            "Foobar".to_string(),
+            "Foo".to_string(),
+            Value::none()
+        )))
     );
 }