MultipleListPlot is replaced by ListPlot and ListLinePlot, which now accept multiple sets of data. Dashing[{Dot,Dash,LongDash}] is replaced with ...
Dividers is an option for Grid and related constructs that specifies where and how to draw divider lines.
Indeterminate is a symbol that represents a numerical quantity whose magnitude cannot be determined.
Mod
(Built-in Mathematica Symbol) Mod[m, n] gives the remainder on division of m by n. Mod[m, n, d] uses an offset d.
Rectangle[{x_min, y_min}, {x_max, y_max}] is a two-dimensional graphics primitive that represents a filled rectangle, oriented parallel to the axes. Rectangle[{x_min, y_min}] ...
RootReduce[expr] attempts to reduce expr to a single Root object.
UnitStep[x] represents the unit step function, equal to 0 for x < 0 and 1 for x >= 0. UnitStep[x_1, x_2, ...] represents the multidimensional unit step function which is 1 ...
WeierstrassP[u, {g_2, g_3}] gives the Weierstrass elliptic function \[WeierstrassP](u; g_2, g_3).
$ImagingDevices gives a list of available imaging devices.
GroupMultiplicationTable[group] gives the multiplication table of group as an array.