I try to understand the smash command, and I made a simple example :

\usepackage{amsmath,amssymb, amsfonts, mathtools}
 \qquad \sum_{\smash{\text{LOOOOONG}}}f(x) 
 \qquad \sum_{\text{LOOOOONG}}f(x) 

But, using smash seems to actually do nothing about the horizontal spacing. I don't understand why this happens (my first source to understand smash and mathclap is macros, A complement to \smash, \llap, and \rlap.

Why isn't the result of the smash more like the mathclap case?

Three ways to deals with long subscript in  sum

  • 3
    \smash only affects vertical space Jan 16, 2023 at 19:02
  • \smash is about the vertical dimension. Jan 16, 2023 at 19:03
  • Oh...! This makes more sense. Thanks a lot. Should I delete my question or keep ip?
    – mahaaaham
    Jan 16, 2023 at 19:04
  • don't edit answers in to the question, it makes the question/answer format hard to follow Jan 16, 2023 at 19:14

1 Answer 1


\smash only affects vertical space, it produces a box with zero height and depth but the natural width of the argument

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