diff --git a/MIL/C09_Differential_Calculus/C09_Differential_Calculus.rst b/MIL/C09_Differential_Calculus/C09_Differential_Calculus.rst
index 51c15f82..a95cf190 100644
--- a/MIL/C09_Differential_Calculus/C09_Differential_Calculus.rst
+++ b/MIL/C09_Differential_Calculus/C09_Differential_Calculus.rst
@@ -2,14 +2,19 @@
 
 .. index:: differential calculus
 
-Differential Calculus
+微分
 =====================
 
-We now consider the formalization of notions from *analysis*,
-starting with differentiation in this chapter
-and turning integration and measure theory in the next.
-In :numref:`elementary_differential_calculus`, we stick with the
-setting of functions from the real numbers to the real numbers,
-which is familiar from any introductory calculus class.
-In :numref:`normed_spaces`, we then consider the notion of a derivative in
-a much broader setting.
+.. Differential Calculus
+.. =====================
+
+.. We now consider the formalization of notions from *analysis*,
+.. starting with differentiation in this chapter
+.. and turning integration and measure theory in the next.
+.. In :numref:`elementary_differential_calculus`, we stick with the
+.. setting of functions from the real numbers to the real numbers,
+.. which is familiar from any introductory calculus class.
+.. In :numref:`normed_spaces`, we then consider the notion of a derivative in
+.. a much broader setting.
+
+ここから **解析学** の概念の形式化について考えていきましょう．この章では微分から始め，次の章では積分と測度論を取り上げます． :numref:`elementary_differential_calculus` では，微積分の入門クラスでおなじみの実数から実数への関数設定に限定します． :numref:`normed_spaces` では導関数の概念をより広い範囲で考えます．