S

sampleImage
saveAllShelves
saveAttrPreset 
saveFluid
saveImage
saveInitialState
saveMenu
savePrefObjects
savePrefs
saveShelf
saveToolSettings
scale
scaleBrushBrightness 
scaleComponents
scaleConstraint
scaleKey
scaleKeyCtx
sceneEditor
sceneUIReplacement
scmh
scriptCtx
scriptEditorInfo
scriptedPanel
scriptedPanelType
scriptJob
scriptNode
scriptTable
scriptToShelf 
scrollField
scrollLayout
sculpt
searchPathArray 
seed
select
selectContext
selectCurveCV 
selectedNodes
selectionConnection
selectKey
selectKeyCtx
selectKeyframeRegionCtx
selectMode
selectPref
selectPriority
selectType
selLoadSettings
separator
setAttr
setAttrEnumResource 
setAttrMapping
setAttrNiceNameResource 
setConstraintRestPosition 
setCustomAttrEnumResource 
setCustomAttrNiceNameResource 
setDefaultShadingGroup
setDrivenKeyframe
setDynamic
setEditCtx
setEditor
setFluidAttr
setFocus
setInfinity
setInputDeviceMapping
setKeyCtx
setKeyframe
setKeyframeBlendshapeTargetWts
setKeyPath
setMenuMode
setNClothRestShape 
setNClothStartFromMesh 
setNodeNiceNameResource 
setNodeTypeFlag
setParent
setParticleAttr
setPfxToPolyCamera 
setPluginResource 
setProject 
setRenderPassType
sets
setStampDensity 
setStartupMessage
setState 
setToolTo
setUITemplate
setXformManip
shadingConnection
shadingGeometryRelCtx
shadingLightRelCtx
shadingNetworkCompare
shadingNode
shapeCompare
shelfButton
shelfLayout
shelfTabLayout
shellField
shortNameOf 
showHelp
showHidden
showManipCtx
showSelectionInTitle
showShadingGroupAttrEditor
showWindow
sign
simplify
sin
singleProfileBirailSurface
size
sizeBytes
skinCluster
skinPercent
smoothCurve
smoothstep
smoothTangentSurface
snap2to2 
snapKey
snapMode
snapshot
snapTogetherCtx
soft
softMod
softModCtx
softSelect
sort
sound
soundControl
source
spaceLocator
sphere
sphrand
spotLight
spotLightPreviewPort
spreadSheetEditor
spring
sqrt
squareSurface
srtContext
stackTrace
startString 
startsWith 
stereoCameraView
stereoRigManager
stitchAndExplodeShell 
stitchSurface
stitchSurfacePoints
strcmp
stringArrayCatenate 
stringArrayContains 
stringArrayCount 
stringArrayInsertAtIndex 
stringArrayIntersector
stringArrayRemove 
stringArrayRemoveAtIndex 
stringArrayRemoveDuplicates 
stringArrayRemoveExact 
stringArrayToString 
stringToStringArray 
strip 
stripPrefixFromName 
stroke
subdAutoProjection
subdCleanTopology
subdCollapse
subdDuplicateAndConnect
subdEditUV
subdiv
subdivCrease
subdivDisplaySmoothness
subdListComponentConversion
subdMapCut
subdMapSewMove
subdMatchTopology
subdMirror
subdToBlind
subdToPoly
subdTransferUVsToCache
substitute
substituteAllString 
substituteGeometry
substring
surface
surfaceSampler
surfaceShaderList
swatchDisplayPort
switchTable
symbolButton
symbolCheckBox
symmetricModelling
sysFile
system

indicates a MEL script