What's the difference between carucage and carucate?

Carucage

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Definition:

• (n.) A tax on every plow or plowland.
• (n.) The act of plowing.

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Carucate

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Definition:

• (n.) A plowland; as much land as one team can plow in a year and a day; -- by some said to be about 100 acres.

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