diff --git a/Siv3D/include/Siv3D/Math.hpp b/Siv3D/include/Siv3D/Math.hpp
index 8962633fd..5c065c87d 100644
--- a/Siv3D/include/Siv3D/Math.hpp
+++ b/Siv3D/include/Siv3D/Math.hpp
@@ -244,21 +244,21 @@ namespace s3d
 		//
 		//////////////////////////////////////////////////
 
-		inline float Modf(float x, float& exp) noexcept;
+		inline float Modf(float x, float& ip) noexcept;
 
-		inline double Modf(double x, double& exp) noexcept;
+		inline double Modf(double x, double& ip) noexcept;
 
-		inline Float2 Modf(Float2 x, Float2& exp) noexcept;
+		inline Float2 Modf(Float2 x, Float2& ip) noexcept;
 
-		inline Float3 Modf(Float3 x, Float3& exp) noexcept;
+		inline Float3 Modf(Float3 x, Float3& ip) noexcept;
 
-		inline Float4 Modf(Float4 x, Float4& exp) noexcept;
+		inline Float4 Modf(Float4 x, Float4& ip) noexcept;
 
-		inline Vec2 Modf(Vec2 x, Vec2& exp) noexcept;
+		inline Vec2 Modf(Vec2 x, Vec2& ip) noexcept;
 
-		inline Vec3 Modf(Vec3 x, Vec3& exp) noexcept;
+		inline Vec3 Modf(Vec3 x, Vec3& ip) noexcept;
 
-		inline Vec4 Modf(Vec4 x, Vec4& exp) noexcept;
+		inline Vec4 Modf(Vec4 x, Vec4& ip) noexcept;
 
 		//////////////////////////////////////////////////
 		//
diff --git a/Siv3D/include/Siv3D/MathParser.hpp b/Siv3D/include/Siv3D/MathParser.hpp
index a1c5d762c..964bb3b4c 100644
--- a/Siv3D/include/Siv3D/MathParser.hpp
+++ b/Siv3D/include/Siv3D/MathParser.hpp
@@ -65,7 +65,7 @@ namespace s3d
 		/// @param name 変数名
 		/// @param value 変数へのポインタ
 		/// @return 変数の登録に成功した場合 true, それ以外の場合は false
-		bool setVaribale(StringView name, double* value);
+		bool setVariable(StringView name, double* value);
 
 		/// @brief 関数を登録します。
 		/// @param name 関数名
diff --git a/Siv3D/include/Siv3D/detail/ImageDecoder.ipp b/Siv3D/include/Siv3D/detail/ImageDecoder.ipp
index 8c8ca6d10..7380f8a7b 100644
--- a/Siv3D/include/Siv3D/detail/ImageDecoder.ipp
+++ b/Siv3D/include/Siv3D/detail/ImageDecoder.ipp
@@ -13,12 +13,12 @@
 
 namespace s3d
 {
-	namespace ImageEncoder
+	namespace ImageDecoder
 	{
-		template <class ImageEncoder>
+		template <class ImageDecoder>
 		bool Add()
 		{
-			return Add(std::make_unique<ImageEncoder>());
+			return Add(std::make_unique<ImageDecoder>());
 		}
 	}
 }
diff --git a/Siv3D/include/Siv3D/detail/ImageEncoder.ipp b/Siv3D/include/Siv3D/detail/ImageEncoder.ipp
index 7380f8a7b..8c8ca6d10 100644
--- a/Siv3D/include/Siv3D/detail/ImageEncoder.ipp
+++ b/Siv3D/include/Siv3D/detail/ImageEncoder.ipp
@@ -13,12 +13,12 @@
 
 namespace s3d
 {
-	namespace ImageDecoder
+	namespace ImageEncoder
 	{
-		template <class ImageDecoder>
+		template <class ImageEncoder>
 		bool Add()
 		{
-			return Add(std::make_unique<ImageDecoder>());
+			return Add(std::make_unique<ImageEncoder>());
 		}
 	}
 }
diff --git a/Siv3D/include/Siv3D/detail/Math.ipp b/Siv3D/include/Siv3D/detail/Math.ipp
index 53284c2f2..7aaf15eac 100644
--- a/Siv3D/include/Siv3D/detail/Math.ipp
+++ b/Siv3D/include/Siv3D/detail/Math.ipp
@@ -307,14 +307,14 @@ namespace s3d
 		//
 		//////////////////////////////////////////////////
 
-		inline float Modf(float x, float& i) noexcept
+		inline float Modf(float x, float& ip) noexcept
 		{
-			return std::modf(x, &i);
+			return std::modf(x, &ip);
 		}
 
-		inline double Modf(double x, double& i) noexcept
+		inline double Modf(double x, double& ip) noexcept
 		{
-			return std::modf(x, &i);
+			return std::modf(x, &ip);
 		}
 
 		SIV3D_MATH_FUNCTION_XYREF(Modf)
diff --git a/Siv3D/src/Siv3D/MathParser/MathParserDetail.cpp b/Siv3D/src/Siv3D/MathParser/MathParserDetail.cpp
index c16f41c9b..12e3f327a 100644
--- a/Siv3D/src/Siv3D/MathParser/MathParserDetail.cpp
+++ b/Siv3D/src/Siv3D/MathParser/MathParserDetail.cpp
@@ -52,7 +52,7 @@ namespace s3d
 		}
 	}
 
-	bool MathParser::MathParserDetail::setVaribale(const StringView name, double* value)
+	bool MathParser::MathParserDetail::setVariable(const StringView name, double* value)
 	{
 		m_errorMessage.clear();
 
diff --git a/Siv3D/src/Siv3D/MathParser/MathParserDetail.hpp b/Siv3D/src/Siv3D/MathParser/MathParserDetail.hpp
index fe8982083..a11009060 100644
--- a/Siv3D/src/Siv3D/MathParser/MathParserDetail.hpp
+++ b/Siv3D/src/Siv3D/MathParser/MathParserDetail.hpp
@@ -38,7 +38,7 @@ namespace s3d
 		bool setConstant(StringView name, double value);
 
 		[[nodiscard]]
-		bool setVaribale(StringView name, double* value);
+		bool setVariable(StringView name, double* value);
 
 		template <class Fty>
 		[[nodiscard]]
diff --git a/Siv3D/src/Siv3D/MathParser/SivMathParser.cpp b/Siv3D/src/Siv3D/MathParser/SivMathParser.cpp
index 5e8cc9951..34cf24264 100644
--- a/Siv3D/src/Siv3D/MathParser/SivMathParser.cpp
+++ b/Siv3D/src/Siv3D/MathParser/SivMathParser.cpp
@@ -46,9 +46,9 @@ namespace s3d
 		return pImpl->setConstant(name, value);
 	}
 
-	bool MathParser::setVaribale(const StringView name, double* value)
+	bool MathParser::setVariable(const StringView name, double* value)
 	{
-		return pImpl->setVaribale(name, value);
+		return pImpl->setVariable(name, value);
 	}
 
 	bool MathParser::setFunction(const StringView name, Fty0 f)