What is anything in three parts or leaves. Specifically: -- (a) A writing tablet in three parts, two of which fold over on the middle part. (b) A picture or altarpiece in three compartments called?

triptych — Anything in three parts or leaves. Specifically: -- (a) A writing tablet in three parts, two of which fold over on the middle part. (b) A picture or altarpiece in three compartments. (Webster's 1913.)

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