octennial
Happening each octave-year
Octennial means occurring every eight years or lasting eight years.
The word appears primarily in formal or technical contexts: octennial celebrations, an octennial review cycle.
It follows the pattern of biennial (two years) and centennial (one hundred years).
Happening only occasionally
- uncommonSeldom occurring or found
- sporadicOccurring irregularly, infrequently
- seldomOn few occasions
- occasionalHappening at intervals
intermittent · irregular · scarce · unusual · exceptional · rare · atypical · isolated
Every ten years
- intervalDuration between two points
- rotationTurning on an axis
- recurrenceReturn of something previous
- periodicityRecurring at regular intervals
frequency · regularity · sequence · epoch · era · phase · duration · timespan
infrequent
Happening only occasionally
occasional · intermittent · irregular · scarce · unusual · exceptional · rare · atypical · isolated · episodic
decennial
Every ten years
- intervalDuration between two points
- rotationTurning on an axis
- recurrenceReturn of something previous
periodicity · frequency · regularity · sequence · epoch · era · phase · duration · timespan · calendar
celebration
Festive event marking occasion
- milestoneNotable event marking progress
- commemorationAct of honoring memory
- jubileeSpecial anniversary observance
ceremony · observance · festival · gala · tribute · memorial · reunion · gathering · banquet · feast
perennial, centennial, biennial, millennial, bicentennial, triennial, quadrennial, septennial, sesquicentennial