Hi I agree with your original thoughts A grid has the pattern of a metal frame that is to be laid over a fire, for cooking. The elements are at 90 degrees A lattice, originally, was made of lathes when building and, for strength, they'd usually be arranged in a diamond pattern However, the word 'lattice' is also used in science and maths, to mean any pattern of elements that are joined up regularly in two or three dimensions. With this usage, I think the pattern can be 90 degrees, or a diamond shape I don't think there's a problem with the plural, 'lattices' at all.
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