RasterSize is an option for Rasterize and related functions that determines the absolute pixel size of the raster generated.
RecordSeparators is an option for Read, Find, and related functions that specifies the list of strings to be taken as delimiters for records.
ReferenceLineStyle is an option for QuantilePlot and similar functions that specifies the style used for the reference line.
RotateLabel is an option for graphics and related functions that specifies whether labels on vertical frame axes should be rotated to be vertical.
RowBox
(Built-in Mathematica Symbol) RowBox[{box_1, box_2, ...}] is a low-level box construct that represents a row of boxes or strings in a notebook expression.
SectorSpacing is an option to PieChart and related functions that specifies radial spacing of sectors.
SoundVolume is an option to Sound and SoundNote and related functions that specifies the relative volume of the sound produced.
SparseArray[{pos_1 -> val_1, pos_2 -> val_2, ...}] yields a sparse array in which values val_i appear at positions pos_i. SparseArray[{pos_1, pos_2, ...} -> {val_1, val_2, ...
SplineDegree is an option for spline functions and graphics primitives that specifies the degree of polynomial basis to use.
StreamStyle is an option to StreamPlot, StreamDensityPlot, and related functions that determines the style to use for drawing streamlines.