What is the meaning of BesselJ with (1,0)?

Questions
1

Hi all

I receive an expression of BesselJ with (0,1). The (0,1) is persented like a power between “BesselJ” and the [].
For example: BesselJ(0,1)[0,3]. The (0,1) is shown as small upper characters.

What is the meaning of this expression as compared to the stardard expression BesselJ[0,3]?

Thanks

2

It’s a derivative with respect to the second argument.

In[2]:= D[f[x, y], y]

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