periodic

Something periodic happens only occasionally, after a "period" of time. Lunch happens every day, after 4th period, so it's safe to say it's periodic. Something periodic doesn't have to happen at regular intervals, though.

The word "period" is the key to the meaning of periodic, because something periodic can happen only after a period of time. Periodic visits to the vet are a good way to make sure that your pet stays healthy. Why not just use "occasional," you ask. Good question. Periodic implies that the thing will continue to happen over and over—periodically. Like comets and victories by the Yankees. These things are reliable, if periodic.

Definitions of periodic
1

adj happening or recurring at regular intervals

“the periodic appearance of the seventeen-year locust”
Synonyms:
periodical
cyclic
marked by repeated cycles
oscillating, oscillatory
having periodic vibrations
diurnal
having a daily cycle or occurring every day
daily, day-after-day, day-by-day, day-to-day
of or belonging to or occurring every day
nightly
happening every night
hebdomadal, hebdomadary, weekly
of or occurring every seven days
biweekly, semiweekly
occurring twice a week
hourly
occurring every hour or payable by the hour
half-hourly
occurring ever half hour
biweekly, fortnightly
occurring every two weeks
annual, yearly
occurring or payable every year
biannual, biyearly, half-yearly, semiannual
occurring or payable twice each year
biennial, biyearly
occurring every second year
triennial
occurring every third year or lasting 3 years
monthly
of or occurring or payable every month
bimestrial, bimonthly
occurring every two months
bimonthly, semimonthly
occurring twice a month
semestral, semestrial
occurring every six months or during every period of six months
midweekly
occurring during the middle of the week
Antonyms:
aperiodic, nonperiodic
not recurring at regular intervals
noncyclic
not having repeated cycles
nonoscillatory
not having periodic vibrations
show more antonyms...

adj recurring or reappearing from time to time

periodic feelings of anxiety”
Synonyms:
occasional
sporadic
recurring in scattered and irregular or unpredictable instances

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