diff --git a/mapytex/calculus/core/MO/monomial.py b/mapytex/calculus/core/MO/monomial.py
index 18a1533..ede5a68 100644
--- a/mapytex/calculus/core/MO/monomial.py
+++ b/mapytex/calculus/core/MO/monomial.py
@@ -27,23 +27,23 @@ class MOstrPower(MO):
         <MOstrPower x^2>
         >>> MOstrPower(3, 1)
         Traceback (most recent call last):
-            ...
+        ...
         mapytex.calculus.core.MO.exceptions.MOError: The variable of a monomial should be convertible into MOstr
         >>> MOstrPower("x", 0)
         Traceback (most recent call last):
-            ...
+        ...
         mapytex.calculus.core.MO.exceptions.MOError: The power of a MOstrPower should be greater than 1
         >>> MOstrPower("x", 1)
         Traceback (most recent call last):
-            ...
+        ...
         mapytex.calculus.core.MO.exceptions.MOError: The power of a MOstrPower should be greater than 1
         >>> MOstrPower("x", -2)
         Traceback (most recent call last):
-            ...
+        ...
         mapytex.calculus.core.MO.exceptions.MOError: The power of a MOstrPower should be greater than 1
         >>> MOstrPower("x", 2.4)
         Traceback (most recent call last):
-            ...
+        ...
         mapytex.calculus.core.MO.exceptions.MOError: The power of a monomial should be a integer
 
         """
@@ -58,11 +58,12 @@ class MOstrPower(MO):
         elif not isinstance(_power._tree, int):
             raise MOError("The power of a monomial should be a integer")
         self._power = _power
- 
+
         _tree = Tree("^",
                      self._variable,
-                     self._power
-                    )
+                     self._power,
+                     )
+
         MO.__init__(self, _tree)
 
     @property
@@ -77,11 +78,12 @@ class MOMonomial(MO):
 
     """ Monomial math object"""
 
-    def __init__(self, coefficient, variable):
+    def __init__(self, coefficient, variable, power=1):
         """ Initiate the MOMonomial
 
         :param coefficient: coefficient of the monomial (a non zero constant)
-        :param variable: variable of the monomial (a MOstr or later a MOSqrt)
+        :param variable: variable of the monomial (a MOstr, a MOstrPower)
+        :param power: degree of the monomial
 
         >>> x = MOstr('x')
         >>> MOMonomial(4, x)
@@ -99,15 +101,28 @@ class MOMonomial(MO):
             raise MOError("The coefficient of a monomial should not be 0")
         self._coefficient = _coefficient
 
-        if not isinstance(variable, (MOstr, MOstrPower)):
-            raise 
-        self._variable = variable
+        if isinstance(variable, MOstrPower):
+            _variable = variable.variable
+            _power = MO.factory(variable.power.value * power)
+        elif isinstance(variable, MOstr):
+            _variable = variable
+            _power = MO.factory(power)
+        else:
+            raise MOError(f"variable need to be a MOstrPower or a MOstr. Got {type(variable)}.")
 
-        _tree = Tree("*",
-                     self._coefficient,
-                     self._variable
+        self._variable = _variable
+        self._power = _power
 
-                    )
+        if self._power == 1:
+            _tree = Tree("*",
+                        self._coefficient,
+                        self._variable
+                        )
+        else:
+            _tree = Tree("*",
+                        self._coefficient,
+                        MOstrPower(self._variable, self._power)
+                        )
 
         MO.__init__(self, _tree)
 
@@ -117,21 +132,15 @@ class MOMonomial(MO):
 
     @property
     def strpower(self):
-        if isinstance(self._variable, MOstr):
-            return self._variable
-        return self._variable
+        return MOstrPower(self._variable, self._power)
 
     @property
     def variable(self):
-        if isinstance(self._variable, MOstr):
-            return self._variable
-        return self._variable.variable
+        return self._variable
 
     @property
     def power(self):
-        if isinstance(self._variable, MOstr):
-            return 1
-        return self._variable.power
+        return self._power
 
 # -----------------------------
 # Reglages pour 'vim'
diff --git a/mapytex/calculus/core/MO/polynomial.py b/mapytex/calculus/core/MO/polynomial.py
index 210669b..ad9c3c6 100644
--- a/mapytex/calculus/core/MO/polynomial.py
+++ b/mapytex/calculus/core/MO/polynomial.py
@@ -10,6 +10,7 @@ from mapytex.calculus.core.tree import Tree
 from .mo import MO, MOnumber, MOstr
 from .exceptions import MOError
 from ..renders import tree2txt, tree2tex
+from .monomial import MOMonomial
 
 __all__ = ["MOpolynomial"]
 
@@ -25,13 +26,13 @@ class MOpolynomial(MO):
 
         :example:
         >>> MOpolynomial('x', [1, 2, 3])
-        3x^2 + 2x + 1
+        <MOpolynomial 3x^2 + 2x + 1>
         >>> MOpolynomial('x', [1, 0, 3])
-        3x^2 + 1
+        <MOpolynomial 3x^2 + 1>
         >>> MOpolynomial('x', {0: 1, 1: 2, 2: 3})
-        3x^2 + 2x + 1
+        <MOpolynomial 3x^2 + 2x + 1>
         >>> MOpolynomial('x', {0: 1, 3: 4})
-        4x^3 + 1
+        <MOpolynomial 4x^3 + 1>
 
 
         """
@@ -41,24 +42,26 @@ class MOpolynomial(MO):
         self._variable = _variable
 
         if isinstance(coefs, dict):
-            _coefs = {MO.factory(d): MO.factory(c) for (d, c) in coefs}
+            _coefs = {MO.factory(d): MO.factory(c) for (d, c) in coefs.items()
+                      if c != 0 }
         elif isinstance(coefs, list):
-            _coefs = {MO.factory(d): MO.factory(c) for (d, c) in enumerate(coefs)}
+            _coefs = {MO.factory(d): MO.factory(c) for (d, c) in enumerate(coefs)
+                      if c != 0 }
         else:
             raise TypeError("Coefs needs to be a dictionnary or a list")
         self._coefs = _coefs
 
         monomials = []
-        for deg, coef in self._coefs:
+        for deg, coef in self._coefs.items():
             if deg == 0:
                 monomials.append(coef)
-            elif deg == 1:
-                monomials.append(coef)
-        value = Tree("^",
-                     self._variable,
-                     self._power
-                    )
-        MO.__init__(self, value)
+            else:
+                monomials.append(
+                    MOMonomial(coef, self._variable, deg)
+                )
+
+        tree = Tree.from_list("+", monomials[::-1])
+        MO.__init__(self, tree)
 
     @property
     def variable(self):