Namespace

ZDoom organizes the lumps in several namespaces which correspond to different types of lumps. This allows to avoid conflicts if several lumps have the same name, but one is, for example, a texture while the other is a sound.

Lumps belong to a namespace or another depending on where they are in the archive. The archive format matters: in sequential archives (such as WAD files), they are delimited by marker lumps; in hierarchized archives, they are in a specific directory.

ZDoom uses the following lump namespaces:

Namespace	Markers	Directory	Notes
Global	Outside of markers	/ (Root directory)
Sprites	S_ or SS_	/Sprites/	Lumps are added to the Sprite image type.
Flats	F_ or FF_	/Flats/	Lumps are added to the Flat image type.
Colormaps	C_	/Colormaps/	Optional
ACS Libraries	A_	/ACS/
Textures	TX_, HI_	/Textures/, /Hires/	Lumps are added to the Override image type.
Blood RAW	N/A	N/A	Files with the .RAW extension in a RFF archive.
Blood SFX	N/A	N/A	Files with the .SFX extension in a RFF archive.
Blood misc	N/A	N/A	Apparently unused
Strife voices	V_	/Voices/	Lumps are automatically assigned svox/<lumpname> as a SNDINFO logical name allowing them to be referenced directly in DIALOGUE scripts.
Hi-Res	HI_	/HiRes/
Sounds	No specific markers	/Sounds/
Patches	No specific markers	/Patches/	Lumps are added to the Wall Patch image type. While not used by the engine, P_ or PP_ markers are often used anyway.
Graphics	No specific markers	/Graphics/	Lumps are added to the Misc Patch image type. The Doom alpha and beta used the L_ marker here.
Music	No specific markers	/Music/
Skin	N/A	N/A	All lumps in an archive containing a S_SKIN lump are placed in a namespace specific to that skin.
Voxels	VX_	/Voxels/

There is also a sort of equivalent of namespaces for images. The texture manager uses the following types:

Name	Description	Namespace	TEXTURES keyword
Any	Graphics that do not fit into any other category.	N/A	N/A
Wall	These have priority over flats when applied on a sidedef.	N/A	WallTexture
Flat	These have priority over walls when applied on a floor or ceiling.	Flats	Flat
Sprite	Needs to be of the form NAMEfa or NAMEfafa, see sprite for more information.	Sprites	Sprite
Wall Patch	The building bricks of composite textures created through TEXTUREx or TEXTURES.	Patches	N/A
Build	See Build tiles for more information.	N/A	N/A
Skin Sprite	These have priority over sprites for players using the corresponding skin.	Skin	N/A
Decal	They are defined in DECALDEF	N/A	N/A
Misc Patch	Miscellaneous graphics	Graphics	Graphic
Font Character	See font formats for more information.	N/A	N/A
Override	Has priority on both flats and walls.	Textures	Texture
Autopage	Automap background.	N/A	N/A
Null	An "empty" texture that is never displayed (e.g., TNT1A0).	N/A	N/A
FirstDefined	The first texture defined in a TEXTUREx lump (e.g., AASTINKY).	N/A	N/A