Here is a list of all namespaces with brief descriptions:

Nbetter_enums
NBFGSOpt
Nboost
Nlogging
Nserialization
Nboost_adaptbx
Npython
NChemicalFeatures
Nconrec
NDistGeom
NForceFields
NCrystalFF
NETKDGForceConsts
NSEQ
NAIO
NMMFF
NUtils
NUFF
NParams
NUtils
NGaussTorsions
NV4
NInvar
NMolTransforms
NQueries
NRankers	Utility functionality used to rank sequences
NRDCatalog
NRDDataManip
NRDDepict
NRDFeatures
NRDGeom
NRDInfoTheory	Class used to rank bits based on a specified measure of information
NRDKit	Std stuff
NAbbreviations
Ncommon_properties
NUtils
NAtomPair
NAtomPairs
NAtropisomers
NCanon
Ndetail
NChirality
Ndetail
NCIPLabeler
NCIPLabeler_detail
Ncommon_properties
Nconstants
NDeprotect
NDescriptors
Ndetail
Ndetail
Ndetails
NDGeomHelpers
NDTags
NEnumerateStereoisomers
Ndetails
NEnumerationStrategyPickler
NEnumerationTypes
NFileParsers
Nschrodinger
NFileParserUtils
NFilterMatchOps
NFMCS
NForceFieldsHelper
Ndetail
NGaussianShape
NGeneralizedSubstruct
NGeneralMolSupplier
NGenericGroups
NMatchers
NLocal
NMACCSFingerprints
NMHFPFingerprints
NFNV
NMMFF
NDefaultParameters
NTools
NMMPA
Ndetail
NMolAlign
Ndetails
NMolDraw2D_detail
NMolDraw2DUtils
NMolEnumerator
Ndetail
Nutils
NMolFragmenter
NMolHash
NMolInterchange
NMolOps	Groups a variety of molecular query and transformation operations
Ndetails
NMolProcessing
Ndetails
NMolShapes
NMolStandardize
Ndefaults
Ndetail
NOperations
NTautomerScoringFunctions
NMorganFingerprint
NMorganFingerprints
NPicklerOps
NPNGData	Tags used for PNG metadata
NQueryOps
NRascalMCES
Ndetails
NRDKitFP
NRDKitFPUtils
NRDTypeTag
Ndetail
NReactionRunnerUtils
NReducedGraphs
NRxnOps
NScaffoldNetwork
Ndetail
NSGroupParsing
NSGroupWriting
NSLNParse
NSmartsWrite
NSmilesParse
NSmilesWrite
Ndetail
NStructureCheck
NSubgraphs
NSubstanceGroupChecks
NSynthonSpaceSearch
Ndetails
NTopologicalTorsion
NUFF
NTools
NUtils
Ndetail
Nv1
Nv2
NCDXMLParser
NFileParsers
NMarvinParser
NReactionParser
NSmilesParse
NRDLog
NRDMIF
NRDNumeric
NAlignments
NEigenSolvers
NRDPickers
NRingUtils
NSmilesParseOps
Ndetail