BlankSequence

__ (two _ characters) or BlankSequence[]

is a pattern object that can stand for any sequence of one or more Wolfram Language expressions.

__h or BlankSequence[h]

can stand for any sequence of one or more expressions, all of which have head h.

Examples

Basic Examples  (3)

A function definition that works with any nonzero number of arguments:

A function definition that works with any nonzero number of real arguments:

A function definition for a symbol followed by any nonzero number of integer arguments:

Introduced in 1988
 (1.0)