What is a diffraction order?

But I came across the term "diffraction order" in literature, and I don't
know what it means.

Does it refer to the areas of diffraction maxima (as in the sin(x)/x
Fraunhoffer pattern)? As in the large central maxima would be zeroth order,
the two on either side would be 1st order, then 2nd order, etc.

Or does it refer to the higher order terms in the expansion of Kirchhoff's
diffraction integral?

What is a diffraction order?

Thanks!
Pete
.

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