expr[[i]] or Part[expr, i] gives the i\[Null]^th part of expr. expr[[-i]] counts from the end. expr[[i, j, ...]] or Part[expr, i, j, ...] is equivalent to expr[[i]][[j]] .... ...

AstronomicalData["name", " property"] gives the value of the specified property of the astronomical object with the specified name.AstronomicalData["name", {"property", ...

Pure functions. When you use functional operations such as Nest and Map, you always have to specify a function to apply. In all the examples above, we have used the "name" of ...

In just one Mathematica command, you can easily specify a calculation that is far too complicated for any computer to do. For example, you could ask for ...

SetVertexWeights[g] assigns random real weights in the range [0, 1] to vertices in g. SetVertexWeights[g, w] assigns the weights in the weight list w to the vertices of g. ...

DialogNotebook[{cell_1, cell_2, ...}] represents a dialog notebook that can be manipulated by the Mathematica front end.

OptionsPattern[] is a pattern object that represents a collection of options given as rules, where the values of the options can be accessed using OptionValue. ...

Mathematica notebooks provide the basic technology that you need to be able to create a very wide range of sophisticated interactive documents. But to get the best out of ...

A possible way of working with permutations is by relating them to the reorderings of the elements of a list. This is the standard point of view in the combinatorial approach ...

You can search for Mathematica help from within Mathematica or on the Wolfram Research websites. The complete documentation is available in every copy of Mathematica as well ...