The apply combinators apply a single quotation to multiple values. The at sign (@) suffixed to these words' names signifies that they are apply combinators.

bi@ ( x y quot -- )

2bi@ ( w x y z quot -- )

tri@ ( x y z quot -- )

2tri@ ( u v w x y z quot -- )

A pair of condition words built from bi@ to test two values:

both? ( x y quot -- ? )

either? ( x y quot -- ? )

All of the apply combinators are equivalent to using the corresponding Spread combinators with the same quotation supplied for every value.