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An upside-down capital pi, the dual of a product.
Also known as: Categorical coproduct, Amalgamated sum, Inverted pi
An inverted capital pi denotes the coproduct — the dual of the product in category theory, which is the disjoint union for sets and the direct sum for vector spaces. Its being the product sign turned over is a statement about duality rather than a typographic accident.
Denotes the coproduct of a family of objects, the categorical dual of the product.
Contexts: Mathematics
Is the disjoint union for sets and the direct sum for vector spaces, so what it names depends on the category.
Contexts: Mathematics
Is drawn as the product sign inverted, which encodes the duality rather than merely decorating it.
Contexts: Mathematics
Two upright strokes joined by a horizontal bar along their feet, forming a capital pi stood on its head.
The dual of the product, and drawn as it inverted.