Relating to or based on the number seven, or arranged in groups of seven.
From Greek 'hepta' (seven) + '-al' (adjective suffix). Used in mathematics, music theory, and formal descriptions of anything organized into sevens since medieval scholarly traditions.
While we often think in tens (decimal) or twelves (musical), some ancient cultures and musical scales actually work in groups of seven—the heptal structure appears in the seven-note musical scale that dominated Western music.
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