merges the associations associ, using the function f to combine values with the same key.


gives an association in which values corresponding to identical keys are combined using f.


represents an operator form of Merge that can be applied to an expression.


  • Merge can operate on any combination of associations and lists of rules.
  • In Merge[expr,f], the function f is applied to lists of values that share the same key.
  • Merge[f][expr] is equivalent to Merge[expr,f].


open allclose all

Basic Examples  (4)

Merge two associations, using Total to combine elements with the same key:

Combine values corresponding to identical keys into lists:

Combine rules with the same left-hand side:

Create a Merge operator:

Scope  (1)

Combine mixed list entries:

Properties & Relations  (1)

Using a combiner function is equivalent to using Map:

Introduced in 2014