A.2.10 The Extent of Input Expressions

Mathematica will treat all input that you give on a single line as being part of the same expression.

Mathematica allows a single expression to continue for several lines. In general, it treats the input that you give on successive lines as belonging to the same expression whenever no complete expression would be formed without doing this.

Thus, for example, if one line ends with =, then Mathematica will assume that the expression must continue on the next line. It will do the same if for example parentheses or other matchfix operators remain open at the end of the line.

If at the end of a particular line the input you have given so far corresponds to a complete expression, then Mathematica will normally begin immediately to process that expression.

You can however explicitly tell Mathematica that a particular expression is incomplete by putting a \ or a (\[Continuation]) at the end of the line. Mathematica will then include the next line in the same expression, discarding any spaces or tabs that occur at the beginning of that line.