diff --git a/lvtc/app/Main.hs b/lvtc/app/Main.hs
index 97f8458..41f8713 100644
--- a/lvtc/app/Main.hs
+++ b/lvtc/app/Main.hs
@@ -7,11 +7,16 @@
 
 module Main (main) where
 
-import Expression
-import Parser
+import Expression (parseAllExpression)
+import Parser (runParser)
+import Alias (proceedAlias)
+
+text :: String
+text = aliasInt ++ aliasRetValue ++ funcMain
+    where
+        aliasInt = "alias int Int;\n"
+        aliasRetValue = "alias retValue 0;\n"
+        funcMain = "fn main () -> int \n{\n    <- retValue;\n};\n"
 
 main :: IO ()
-main = print $ runParser (parseExpresion)
-    "fn main () -> Int \n{\n    <- 0;\n};\n"
--- main = print $ runParser (parseExpresion) "alias abc def;\n"
--- main = print $ runParser (parseExpresion) "// this is a comment\n"
+main = print $ runParser (proceedAlias <$> parseAllExpression) text
diff --git a/lvtc/lvtc.cabal b/lvtc/lvtc.cabal
index 2f3ff1c..76130c0 100644
--- a/lvtc/lvtc.cabal
+++ b/lvtc/lvtc.cabal
@@ -25,6 +25,7 @@ source-repository head
 
 library
   exposed-modules:
+      Alias
       Expression
       Lib
       Parser
diff --git a/lvtc/src/Alias.hs b/lvtc/src/Alias.hs
new file mode 100644
index 0000000..fafd5f2
--- /dev/null
+++ b/lvtc/src/Alias.hs
@@ -0,0 +1,80 @@
+{-
+-- EPITECH PROJECT, 2023
+-- Leviator compiler
+-- File description:
+-- Alias
+-}
+
+module Alias (
+    proceedAlias,
+) where
+
+import Expression
+import Parser
+import ParseUtil
+import Control.Applicative
+
+data Alias = Alias String String
+
+instance Show Alias.Alias where
+    show (Alias.Alias str1 str2) = "ALIAS `" ++ str1 ++ "`:`" ++ str2 ++ "`"
+
+parseAliasKeyword :: Parser String
+parseAliasKeyword = parseString "alias "
+
+parseAliasName :: Parser String
+parseAliasName = parseAllCharUntil " "
+
+parseAliasValue :: Parser String
+parseAliasValue = parseAllCharUntil ";\n"
+
+parseAlias' :: Parser String
+parseAlias' = (parseAliasKeyword *> parseAliasName <* many (parseChar ' '))
+
+parseAlias :: Parser Alias.Alias
+parseAlias = Parser f
+    where
+        f str = case runParser parseAlias' str of
+            Nothing -> Nothing
+            Just (key, xs) -> case runParser parseAliasValue xs of
+                Nothing -> Nothing
+                Just (value, ys) -> Just (Alias.Alias key value, ys)
+
+replaceAliasInString :: Alias.Alias -> String -> String
+replaceAliasInString _ [] = []
+replaceAliasInString (Alias.Alias key value) (x:xs)
+    | take (length key) (x:xs) == key =
+        value ++ replaceAliasInString
+                    (Alias.Alias key value)
+                    (drop (length key) (x:xs))
+    | otherwise = x : replaceAliasInString (Alias.Alias key value) xs
+
+replaceAlias :: Alias -> [Expression] -> [Expression]
+replaceAlias _ [] = []
+replaceAlias alias ((Expression.Alias _):xs) =
+    replaceAlias alias xs
+replaceAlias (Alias.Alias key value) ((Expression.Function str):xs) =
+    (Expression.Function (replaceAliasInString (Alias.Alias key value) str))
+    : (replaceAlias (Alias.Alias key value) xs)
+replaceAlias (Alias.Alias key value) ((Expression.Comment str):xs) =
+    (Expression.Comment (replaceAliasInString (Alias.Alias key value) str))
+    : (replaceAlias (Alias.Alias key value) xs)
+
+replaceAllAlias :: [Alias] -> [Expression] -> [Expression]
+replaceAllAlias [] exprs = exprs
+replaceAllAlias _ [] = []
+replaceAllAlias (x:xs) exprs = replaceAllAlias xs newExprs
+    where
+        newExprs = replaceAlias x exprs
+
+getListAlias :: [Expression] -> [Alias]
+getListAlias [] = []
+getListAlias ((Expression.Alias str):xs) = case runParser parseAlias str of
+    Just (alias, _) -> alias : getListAlias xs
+    Nothing -> getListAlias xs
+getListAlias (_:xs) = getListAlias xs
+
+proceedAlias :: [Expression] -> [Expression]
+proceedAlias exprs = replaceAllAlias lstAlias exprs
+    where
+        lstAlias = getListAlias exprs
diff --git a/lvtc/src/Expression.hs b/lvtc/src/Expression.hs
index db13e4e..370c4c4 100644
--- a/lvtc/src/Expression.hs
+++ b/lvtc/src/Expression.hs
@@ -39,7 +39,7 @@ countBracketsForFunction n ('\\':_:xs) = countBracketsForFunction n xs
 countBracketsForFunction n (_:xs) = countBracketsForFunction n xs
 
 parseFunction' :: Parser Expression
-parseFunction' = Function <$> ((++) <$>
+parseFunction' = (\x -> Function (x ++ "\n};\n")) <$> ((++) <$>
                     (parseString "fn " <|> parseString "export fn") <*>
                     parseAllCharUntil "\n};\n")
 
@@ -55,11 +55,13 @@ parseFunction = Parser f
 
 parseAlias :: Parser Expression
 parseAlias =
-    Alias <$> ((++) <$> parseString "alias " <*> parseAllCharUntil ";\n")
+    (\x -> Alias (x ++ ";\n")) <$>
+        ((++) <$> parseString "alias " <*> parseAllCharUntil ";\n")
 
 parseComment :: Parser Expression
 parseComment =
-    Comment <$> ((++) <$> parseString "//" <*> parseAllCharUntil "\n")
+    (\x -> Comment (x ++ "\n")) <$>
+        ((++) <$> parseString "//" <*> parseAllCharUntil "\n")
 
 parseExpresion :: Parser Expression
 parseExpresion = parseAlias <|> parseFunction <|> parseComment
diff --git a/lvtc/src/ParseUtil.hs b/lvtc/src/ParseUtil.hs
index 11c2a40..20f020c 100644
--- a/lvtc/src/ParseUtil.hs
+++ b/lvtc/src/ParseUtil.hs
@@ -70,4 +70,4 @@ parseAllCharUntil str = Parser f
         f [] = empty
         f (x:xs) = case runParser (parseString str) (x:xs) of
                 Nothing -> runParser ((x :) <$> parseAllCharUntil str) xs
-                Just (y, ys) -> Just (y, ys)
+                Just (_, ys) -> Just ([], ys)
diff --git a/lvtc/test/Spec.hs b/lvtc/test/Spec.hs
index 4b717e0..4c9879c 100644
--- a/lvtc/test/Spec.hs
+++ b/lvtc/test/Spec.hs
@@ -10,6 +10,7 @@ import Test.Tasty.HUnit
 
 import Expression
 import Parser
+import Alias
 
 main :: IO ()
 main = defaultMain tests
@@ -18,7 +19,8 @@ tests :: TestTree
 tests = testGroup "Leviator Tests - Compiler"
     [
         utParserExpression,
-        utParserExpressions
+        utParserExpressions,
+        utAlias
     ]
 
 testParserHelper :: String -> String -> Expression -> IO ()
@@ -61,7 +63,7 @@ utParserExpression = testGroup "Parse Expression"
       testParserHelper
         "alias abc def;\n"
         ""
-        (Alias "alias abc def;\n")
+        (Expression.Alias "alias abc def;\n")
   , testCase "alias bad formated (no end `\\n`)" $
       testParserHelperFail
         "alias abc def;"
@@ -125,16 +127,42 @@ utParserExpressions = testGroup "Parse Expressions"
       testParserHelpers
         "alias abc def;\nalias def def;\n"
         ""
-        [Alias "alias abc def;\n", Alias "alias def def;\n"]
+        [Expression.Alias "alias abc def;\n", Expression.Alias "alias def def;\n"]
   , testCase "alias multiline" $
       testParserHelpers
         "alias abc def\nefg hij;\n"
         ""
-        [Alias "alias abc def\nefg hij;\n"]
+        [Expression.Alias "alias abc def\nefg hij;\n"]
 -- comment
   , testCase "comment" $
       testParserHelpers
         "// this is a comment\nalias abc def;\n"
         ""
-        [Comment "// this is a comment\n", Alias "alias abc def;\n"]
+        [Comment "// this is a comment\n", Expression.Alias "alias abc def;\n"]
+  ]
+
+utAlias :: TestTree
+utAlias = testGroup "Alias"
+  [
+    testCase "alias" $
+      assertEqual "alias"
+        [
+            Expression.Function "fn main() -> Int \n{\n    <- 0;\n};"
+        ]
+        (proceedAlias [
+            Expression.Alias "alias int Int;\n",
+            Expression.Alias "alias retValue 0;\n",
+            Expression.Function "fn main() -> int \n{\n    <- retValue;\n};"
+        ])
+  , testCase "nested alias" $
+      assertEqual "alias nested"
+        [
+            Expression.Function "fn main() -> Int \n{\n    <- 0;\n};"
+        ]
+        (proceedAlias [
+            Expression.Alias "alias int INT;\n",
+            Expression.Alias "alias retValue 0;\n",
+            Expression.Alias "alias INT Int;\n",
+            Expression.Function "fn main() -> int \n{\n    <- retValue;\n};"
+        ])
   ]