sexennis

sex (“six”) +‎ annus (“year”) +‎ -is (suffix forming compound adjectives).

• (Classical Latin) IPA^(key): /sekˈsen.nis/, [s̠ɛkˈs̠ɛnːɪs̠]
• (modern Italianate Ecclesiastical) IPA^(key): /sekˈsen.nis/, [seɡˈzɛnːis]

sexennis (neuter sexenne); third-declension two-termination adjective

1. six years old
2. of six years, lasting six years

Third-declension two-termination adjective.

• biennis, triennis, quadriennis, quinquennis, septuennis, octennis, novennis, decennis, undecennis, duodecennis, tridecennis, quattuordecennis, quindecennis, sedecennis, septendecennis, duodevicennis, undevicennis, vicennis, tricennis, quadragennis, quinquagennis, sexagennis, septuagennis, octogennis, nonagennis, centennis, ducentennis, trecentennis, quadringentennis, quingentennis, sescentennis, septingentennis, octingentennis, nongentennis, millennis

• “sexennis”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• sexennis in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette, page 1434/2.
• “sexennis” on page 1752/1 of the Oxford Latin Dictionary (1st ed., 1968–82)