What's the difference between hognut and pignut?

Hognut

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Definition:

• (n.) The pignut.
• (n.) In England, the Bunium flexuosum, a tuberous plant.

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Pignut

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Definition:

• (n.) See Groundnut (d).
• (n.) The bitter-flavored nut of a species of hickory (Carya glabra, / porcina); also, the tree itself.

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