Activate

Activate[expr] replaces all instances of Inactive[f] in expr with f.

Activate[expr, patt] replaces only instances of Inactive[f] for which f matches the pattern patt.

Examples

Activate an inactive expression:

Activate[Inactive[Plus][2, 3]]
(* 5 *)

Selectively activate only certain functions:

Activate[Inactive[Plus][Inactive[Times][2, 3], 4], Times]
(* Inactive[Plus][6, 4] *)

Please visit the official Wolfram Language Reference for more details.