Relating to or having the nature of a creed; based on or expressing a system of religious or philosophical beliefs.
From 'creed' plus the adjective suffix '-al'. Creed comes from Latin 'credo' (I believe), originally used for formal statements of Christian faith.
The jump from 'creed' to 'creedal' mirrors how Latin root words naturally spawn adjectives—this same '-al' suffix turns 'culture' into 'cultural' and 'nature' into 'natural'!
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