Definition:Set Union/Historical Note

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Historical Note on Set Union

The concept of set union, or logical addition, was stated by Leibniz in his initial conception of symbolic logic.

The symbol $\cup$, informally known as cup, was first used by Hermann Günter Grassmann in Die Ausdehnungslehre from $1844$.

However, he was using it as a general operation symbol, not specialized for set union.

It was Giuseppe Peano who took this symbol and used it for union, in his $1888$ work Calcolo geometrico secondo l'Ausdehnungslehre di H. Grassmann.

Peano also created the large symbol $\bigcup$ for general union of more than two sets.

This appeared in his Formulario Mathematico, 5th ed. of $1908$.