A comma replaces the word "and" and when I told my Oxford-comma-loving husband that, he asked me where I heard it. I replied in high school and college grammar classes. I should reveal that he is a professional writer too, and a good one.
I will give him credit that he brought this quote to me, supporting my belief and opposite to his.
"For example, in such enumeration as 'French, German, Italian and Spanish', the two commas take the place of 'ands': there is no comma after Italian', because, with 'and', it would be otiose." This was from Fowler's Modern English Usage.
I have to admit I had to look up the word 'otiose' something I rarely have to do, which is humbling.
Merriman-Webster defines otiose as producing no use result, futile, functionless.
That one of the few disagreements he and I have are over the Oxford comma.
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