Sequence[expr_1, expr_2, ...] represents a sequence of arguments to be spliced automatically into any function.

SmithWatermanSimilarity[u, v] gives a number representing the Smith\[Dash]Waterman similarity between strings or vectors u and v.

Spacer[w] displays as a spacer w printer's points wide.Spacer[{w, h}] displays as a spacer w points wide and a total of h points high.Spacer[{w, h, dh}] makes the spacer ...

SpanFromAbove is a symbol that can appear at a particular position in a Grid or related construct to indicate that the corresponding position is occupied by a spanning ...

SqrtBox[x] is a low-level box construct that represents the displayed object Sqrt[x] in notebook expressions.

StabilityMargins is an option to frequency response plots such as BodePlot, NyquistPlot, and NicholsPlot that specifies the gain and phase margins to be shown on the plot.

Stack[] shows the current evaluation stack, giving a list of the tags associated with evaluations that are currently being done. Stack[pattern] gives a list of expressions ...

StatusArea[expr, string] displays string in the status area of the current notebook when the mouse pointer is in the region where expr appears.

StepMonitor is an option for iterative numerical computation functions that gives an expression to evaluate whenever a step is taken by the numerical method used.

Subscript[x, y] is an object that formats as x_y. Subscript[x, y_1, y_2, ...] formats as x Subscript[y, 1], Subscript[y, 2], ....