There are four kinds of bracketing used in Mathematica. Each kind of bracketing has a very different meaning. It is important that you remember all of them. The four kinds of ...

CatalanNumber and Subfactorial have been added to the built-in Mathematica kernel. CatalanNumber and Subfactorial can now be evaluated numerically for noninteger arguments. ...

ArcCsch[z] gives the inverse hyperbolic cosecant csch -1 (z) of the complex number z.

DistributionParameterQ[dist] yields True if dist is a valid distribution, and yields False otherwise.

Divisible[n, m] yields True if n is divisible by m, and yields False if it is not.

FindGraphIsomorphism[g_1, g_2] finds an isomorphism that maps the graph g_1 to g_2 by renaming vertices.

SphericalHarmonicY[l, m, \[Theta], \[Phi]] gives the spherical harmonic Y_l^m(\[Theta], \[Phi]).

While[test, body] evaluates test, then body, repetitively, until test first fails to give True.

Power series are represented in Mathematica as SeriesData objects. The power series is printed out as a sum of terms, ending with O[x] raised to a power. Internally, however, ...

lhs = rhs evaluates rhs and assigns the result to be the value of lhs. From then on, lhs is replaced by rhs whenever it appears. {l_1, l_2, ...} = {r_1, r_2, ...} evaluates ...