expr //. rules repeatedly performs replacements until expr no longer changes.
RogersTanimotoDissimilarity[u, v] gives the Rogers\[Dash]Tanimoto dissimilarity between Boolean vectors u and v.
RootApproximant[x] converts the number x to one of the "simplest" algebraic numbers that approximates it well.RootApproximant[x, n] finds an algebraic number of degree at ...
RotateRight[expr, n] cycles the elements in expr n positions to the right. RotateRight[expr] cycles one position to the right. RotateRight[expr, {n_1, n_2, ...}] cycles ...
SampledSoundFunction[f, n, r] is a sound primitive that represents a sound whose amplitude sampled r times a second is generated by applying the function f to successive ...
SectorOrigin is an option to PieChart and related functions that specifies where sectors should start.
SectorSpacing is an option to PieChart and related functions that specifies radial spacing of sectors.
SelfLoopStyle is an option for GraphPlot and related functions that specifies how to draw self-loops that connect a vertex to itself.
SpheroidalJoiningFactor[n, m, \[Gamma]] gives the spheroidal joining factor with degree n and order m.
StringReverse["string"] reverses the order of the characters in " string".