septenary

adj

1. (not-comparable)Consisting of or containing seven.
2. (not-comparable)Of seventh rank or order.

   “... indeed if further evidence than that of bestial and savage counting were required to show that finger-numeration and the quinary system were not primeval, it would be afforded by the development of the senary-septenary system in so many lands.”

3. (not-comparable)Lasting seven years; continuing seven years.

   “Septenary penance.”

noun

1. A group of seven things.
2. A period of seven years.

   “This idea was based on the doctrine that a man's body changed its character every seven years and that his life was thus made up of ‘septenaries’.”

3. The seven notes of the diatonic scale.