centenary

at fixed intervals

(of a disease or physical condition) continuing for a long time

incessant, never-ending

repeated at regular intervals

recurrent

often happening

common, repeated

done or occurring every hour

at fixed intervals

pausing or stopping at intervals

irregular, sporadic

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

occurring or appearing at regular intervals

at fixed intervals

going on for a long time or without stopping

continual, lasting

happening during a particular season; changing with the seasons

irregular, sporadic