#periodic_event__recurrent_event__recurrentevent  an event that recurs at intervals
  supertype:  happening__occurrence__natural_event__naturalevent  an event that happens
  subtype:  migration.periodic_event  the periodic passage from one region to another for feeding or breeding
  subtype:  cycle.periodic_event  a single complete execution of a periodically repeated phenomenon: "a year constitutes a cycle of the seasons"
     subtype:  cardiac_cycle__cardiaccycle  the complete cycle of events in the heart from the beginning of one heart beat to the beginning of the next; an electrical impulse in conducted through the heart muscle that constricts the atria which is followed by constriction of the ventricles; "the cardiac cycle can be shown on an electrocardiogram"
     subtype:  Carnot_cycle__Carnot's_ideal_cycle  a cycle (of expansion and compression) of an idealized reversible heat engine that does work without loss of heat
     subtype:  pass.cycle  one complete cycle of operations (as by a computer); "it was not possible to complete the computation in a single pass"
     subtype:  menstrual_cycle__menstrualcycle  a recurring cycle (beginning at menarche and ending at menopause) in which the endometrial lining of the uterus prepares for pregnancy; if pregnancy does not occur the lining is shed at menstruation; "the average menstrual cycle is 28 days"
  subtype:  repeat__repetition  an event that repeats; "the events today were a repeat of yesterday's"
     subtype:  sequence.repeat  several repetitions of a melodic phrase in different keys
     subtype:  cycle  a periodically repeated sequence of events: "a cycle of reprisal and retaliation"
        subtype:  samsara  (Hinduism; Buddhism) the endless cycle of birth and suffering and death and rebirth
     subtype:  replay__rematch  something (especially a game) that is played again
     subtype:  recurrence__return  happening again (especially at regular intervals); "the return of spring"
        subtype:  atavism__throwback  a reappearance of an earlier characteristic
        subtype:  flashback.recurrence  an unexpected but vivid recurrence of a past experience (especially a recurrence of the effects of an hallucinogenic drug taken much earlier)
  subtype:  sunrise  the daily event of the sun rising above the horizon
  subtype:  sunset  the daily event of the sun sinking below the horizon
  subtype:  undulation__wave  (physics) a progressive disturbance propagated without displacement of the medium itself
     subtype:  gravity_wave__gravitywave__gravitation_wave__gravitationwave  (physics) a wave that is hypothesized to propagate gravity and to travel at the speed of light
     subtype:  sine_wave  a wave whose waveform resembles a sine curve
     subtype:  vibration__oscillation  (physics) a regular variation in value about a mean
        subtype:  ripple  (electronics) an oscillation of small amplitude imposed on top of a steady value
        subtype:  transient  (physics) a short-lived oscillation in a system caused by a sudden change of voltage or current or load
        subtype:  beat.vibration  a single pulsation of an oscillation produced by adding two waves of different frequencies; has a frequency equal to the difference between the two oscillations
        subtype:  resonance.vibration  a vibration of large amplitude produced by a relatively small vibration near the same frequency of vibration as the natural frequency of the resonating system
        subtype:  sympathetic_vibration__sympatheticvibration  (physics) vibration produced by resonance
     subtype:  fluctuation  a wave motion; "the fluctuations of the sea"
     subtype:  seiche  a wave on the surface of a lake or landlocked bay; caused by atmospheric or seismic disturbances
     subtype:  standing_wave__stationary_wave  a wave (as a sound wave in a chamber or an electromagnetic wave in a transmission line) in which the ratio of its instantaneous amplitude at one point to that at any other point does not vary with time
     subtype:  sound_wave__soundwave__acoustic_wave  (acoustics) a wave that transmits sound
        subtype:  air_wave__airwave  a sound wave that is transmitted via air
        subtype:  shock_wave__shockwave  a region of high pressure travelling through a gas at a high velocity
           subtype:  sonic_boom__sonicboom  an explosive sound caused by the shock wave of an airplane traveling faster than the speed of sound; "a sonic boom follows an aircraft as a wake follows a ship"
     subtype:  waveform__wave_form__wave_shape  the shape of a wave illustrated graphically by plotting the values of the period quantity against time
     subtype:  pulsing__pulse__impulse  (electronics) a sharp transient wave in the normal electrical state (or a series of such transients); "the pulsations seemed to be coming from a star"
     subtype:  flapping__flap__flutter__fluttering  the motion made by flapping up and down
  subtype:  pulsation__heartbeat__beat  the rhythmic contraction and expansion of the arteries with each beat of the heart; "he could feel the beat of her heart"
     subtype:  diastole  the widening of the chambers of the heart between two contractions when the chambers fill with blood
     subtype:  systole  the contraction of the chambers of the heart (especially the ventricles) to drive blood into the aorta and pulmonary artery
     subtype:  pounding__throb__throbbing  an instance of rapid strong pulsation (of the heart); "he felt a throbbing in his head"
  subtype:  tide  the periodic rise and fall of the sea level under the gravitational pull of the moon
     subtype:  high_tide__high_water__highwater  the tide when the water is highest
        subtype:  direct_tide  the occurrence of high tide on one side of the earth coinciding with high tide on the opposite side
        subtype:  neap_tide__neap  a less than average tide occurring at the first and third quarters of the moon
        subtype:  springtide  a greater than average tide occurring during the new and full moons
     subtype:  low_tide__lowtide__low_water__lowwater  the lowest (farthest) ebb of the tide
     subtype:  ebbtide  the tide while water is flowing out
     subtype:  rising_tide__flood_tide__floodtide  the occurrence of incoming water (between a low tide and the following high tide)
     subtype:  slack_water__slack_tide__slacktide  the occurrence of relatively still water at the turn of the (low) tide

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