入れ子名前空間で[expected identifier before numeric constant] エラーの原因が知りたい。

提示コードですがヘッダーのみの以下のヘッダーファイルで expected identifier before numeric constant エラーが発生します。これはなぜでしょうか？原因がわかりません。

expected identifier before numeric constant

日本語翻訳

数値定数の前に予期される識別子

#ifndef VERTEX_DATA_HPP_
#define VERTEX_DATA_HPP_

/*#########################################################################
# Vertex

説明
	頂点情報
###########################################################################*/


namespace FrameWork 
{
	namespace 2D
	{
		typedef struct vertex_attribute
		{
			GLfloat position[2];
			GLfloat uv[2];
			GLfloat normal[3];
			GLfloat color[4];
		}VertexAttribute;
	}
}
#endif

$ make
g++ -std=c++2a -I/usr/local/include/freetype2 -I/usr/include/libpng16 -I/usr/local/include -pthread -c -MMD -MP source/Render.cpp -o obj/Render.o
In file included from source/../header/Render.hpp:13,
                 from source/Render.cpp:1:
source/../header/VertexData.hpp:14:12: エラー: expected identifier before numeric constant
  namespace 2D
            ^~
source/../header/VertexData.hpp:14:12: エラー: expected unqualified-id before numeric constant
In file included from source/../header/Render.hpp:14,
                 from source/Render.cpp:1:
source/../header/Transform.hpp:10:12: エラー: expected identifier before numeric constant
  namespace 2D
            ^~
source/../header/Transform.hpp:10:12: エラー: expected unqualified-id before numeric constant
In file included from source/Render.cpp:1:
source/../header/Render.hpp:18:12: エラー: expected identifier before numeric constant
  namespace 2D
            ^~
source/../header/Render.hpp:18:12: エラー: expected unqualified-id before numeric constant
In file included from source/Render.cpp:4:
source/../header/Help.hpp:15:12: エラー: expected identifier before numeric constant
  namespace 2D
            ^~
source/../header/Help.hpp:15:12: エラー: expected unqualified-id before numeric constant
source/Render.cpp:9:12: エラー: expected unqualified-id before numeric constant
 FrameWork::2D::Render::Render()
            ^~
source/Render.cpp:23:12: エラー: expected unqualified-id before numeric constant
 FrameWork::2D::Render::~Render()
            ^~
make: *** [Makefile:18: obj/Render.o] エラー 1
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