septennial

Adjective

sep=ten=ni=al

CIDE DICTIONARY

septennial, a. [L. septennium a period of seven years; septem seven + annus year. See Seven, and Annual.].

Lasting or continuing seven years; as, septennial parliaments. [1913 Webster]
Happening or returning once in every seven years; as, septennial elections in England. [1913 Webster]

septennial, adj.
1 lasting for seven years.
2 recurring every seven years.

Etymology

LL septennis f. L septem seven + annus year