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The Four Kinds of Bracketing in Mathematica

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.
(term)parentheses for grouping
f[x]square brackets for functions
{a,b,c}curly braces for lists
v[[i]]double brackets for indexing (Part)

The four kinds of bracketing in Mathematica.

When the expressions you type in are complicated, it is often a good idea to put extra space inside each set of brackets. This makes it somewhat easier for you to see matching pairs of brackets. is, for example, easier to recognize than .