This professor is using this symbol to denote the input space.

enter image description here

an X with bars at the top and bottom, is there a latex font correspond to the symbol?

I've tried Detexify,

enter image description here

didn't get any luck.

  • You could try detexify.kirelabs.org/classify.html to draw your symbol. I did it, but was not able to get any hints. Good luck!
    – Jan
    Dec 14, 2019 at 8:37
  • 1
    That’s not a special symbol, but just an X. I’ve seen several people writing it like that on the blackboard, probably for distinguishing it from \times.
    – egreg
    Dec 14, 2019 at 8:59
  • @egreg So, is there a latex symbol to render that in computer?
    – JJJohn
    Dec 14, 2019 at 9:04
  • @JJJohn Not sure what you mean: you render it with X.
    – egreg
    Dec 14, 2019 at 9:33
  • 1
    By the way, if you notice, in the last line the X has no bars and it represents exactly the same quantity.
    – egreg
    Mar 13, 2020 at 23:16

2 Answers 2


Using the package romanbar (\usepackage{romanbar}), it is possible to obtain an X with bars at the top and bottom. I hope that the symbol is good for you.

\Romanbar{10}, \verb|It is used in text-mode|

\[\abs{\Romanx}=2^{1000}, \verb|It is used in math-mode|\]

enter image description here


There is no such symbol on the blackboard. It's simply an uppercase “X” that some people adorn on the blackboard with bars perhaps in order to distinguish it from ⨉.

If you look closely, the same symbol for the cardinality of X is used at the exponent of 2, and the X has no ornament.

Nothing special: it's just an X.

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