It is common in machine learning papers to see notation such as

$$X \in \mathcal{X}$$

where both variables are "X" but one is in calligraphy (\mathcal in typesetting). When reading a document using such notation, the difference between variables is obvious, but orally "X in X" may be confusing to some listeners.

Is there a standard (or even common) parlance/notation used to refer to calligraphic letters orally?

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    $\begingroup$ I heard that someone is saying ‘curl X’, but I am not sure if it is for the frak font or the other one. $\endgroup$ – J1U Dec 10 '19 at 7:11
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    $\begingroup$ I have most often heard "script X." Strictly speaking, if one were to be faithful to Latex's nomenclature it should be "calligraphic X" for \mathcal{X} $\mathcal{X}$, and "script X" for \mathscr{X} $\mathscr{X}$ but I don't know if people make this distinction in real life. $\endgroup$ – angryavian Dec 10 '19 at 7:20
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    $\begingroup$ @J1U I would think that "curl $X$" could be dangerous, as the curl of a vector field is a thing. Are you sure that they weren't saying "cal $X$"? $\endgroup$ – Xander Henderson Dec 10 '19 at 14:15
  • $\begingroup$ @XanderHenderson I am still not sure, but maybe it was ‘curly X’, not ‘curl X’. $\endgroup$ – J1U Dec 10 '19 at 14:17

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