hebdomad

noun3

1. •
   A group of seven world-creating archons (supernatural beings) often regarded as somewhat hostile; also, a term of address for the Demiurge (“a being sometimes seen as the creator of evil”).
2. •
   A period of seven days; a week.
3. •
   (no longer used) A group of seven.

   • The Babylonian race will hold the Roman state in its power for a threefold cycle hebdomad of years. Thereafter the Romans will enslave the Persians in the fifth hebdomad of years. — 2018