centenary
at fixed intervals
(of a disease or physical condition) continuing for a long time
incessant, never-ending
happening very often or with only short breaks
constant, incessant
often happening
common, repeated
regular, usual; having a habit mentioned
usual, established
that stays in one's mind, thoughts
unforgettable
done or occurring every hour
at fixed intervals
pausing or stopping at intervals
irregular, sporadic
contrary to rules, to what is normal and established
random, variable
(uninteresting because) unchanging, without variety
all the same, remaining the same
done, happening etc once a month; valid for one month
at fixed intervals
of, concerning, an orbit; a circular motorway round a city (e.g. the London Orbital)
at fixed intervals
continuing throughout the whole year; lasting for a very long time; living for more than two years
enduring, perpetual
occurring or appearing at regular intervals
at fixed intervals
going on for a long time or without stopping
continual, lasting
coming, doing something, at the agreed or fixed time
on time
happening during a particular season; changing with the seasons
irregular, sporadic
an informal meeting of friends to sing songs together
all the same, remaining the same
not stopping
continual