You can tell a lot about what "type" of expression something is by looking at its head. Thus, for example, an integer has head Integer, while a list has head List. In a ...

Four underlying types of numbers are built into Mathematica. Intrinsic types of numbers in Mathematica. Rational numbers always consist of a ratio of two integers, reduced to ...

FindPermutation[expr] gives a permutation that produces expr by permuting Sort[expr].FindPermutation[expr 1, expr 2] gives a permutation that converts expr_1 to expr_2 for ...

AllowGroupClose is an option for Cell that specifies whether a cell group can be closed normally.

TraceOriginal is an option for Trace and related functions which specifies whether to test the form of each expression before its head and arguments are evaluated.

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

Delete[expr, n] deletes the element at position n in expr. If n is negative, the position is counted from the end. Delete[expr, {i, j, ...}] deletes the part at position {i, ...

Complex is the head used for complex numbers.

ExactNumberQ[expr] returns True if expr is an exact real or complex number, and returns False otherwise.

Ways to label two-dimensional plots. Here is a plot, using the default Axes->True. Setting Frame->True generates a frame with axes, and removes tick marks from the ordinary ...