An alternate or variant spelling of abscissa (the horizontal axis in a coordinate system) or a liturgical architectural element.
From Latin absis or absidia, relating to the apse of a church (a semicircular alcove), or confusion with abscissa from Latin abscindere (to cut off). The spelling varies due to Latin manuscripts and medieval copying.
The word absis shows how medieval scribes weren't consistent—multiple spellings of the same word coexisted for centuries because there was no printing press to standardize things, making historical Latin texts delightfully messy.
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