Infix

Infix[f[e1, e2, ...]] prints with f in default infix form: e1fe2fe3....

Infix[expr, h] prints with arguments separated by h.

Examples

Default infix form:

Infix[f[a, b, c]]
(* a ~f~ b ~f~ c *)

Custom separator:

Infix[Plus[a, b, c], " + "]

Please visit the official Wolfram Language Reference for more details.