Cathedral

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Middle English (as an adjective, the noun being short for cathedral church ‘the church which contains the bishop's throne’): from late Latin cathedralis, from Latin cathedra ‘seat’, from Greek kathedra .

wiktionary

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From Middle English cathedral, chathedral, cathiderall, from Old French[Term?], from Latin cathedrālis, from cathedra +‎ -ālis.

Ellipsis of  cathedral church, from Middle Englishchirche cathederall, cathedrall chirch,  calque of Late Latinecclēsia cathedrālis(“church having a bishop's seat”), from Latin ecclēsia +‎  cathedrālis. 

etymonline

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cathedral (n.)

1580s, "church of a bishop," from phrase cathedral church (c. 1300), partially translating Late Latin ecclesia cathedralis "church of a bishop's seat," from Latin cathedra "an easy chair (principally used by ladies)," also metonymically, as in cathedrae molles "luxurious women;" also "a professor's chair;" from Greek kathedra "seat, bench," from kata "down" (see cata-) + hedra "seat, base, chair, face of a geometric solid," from PIE root *sed- (1) "to sit."

It was born an adjective, and attempts to force further adjectivization onto it in 17c. yielded cathedraical (1670s), cathedratic (1660s), cathedratical (1660s), after which the effort seems to have been given up.