1. A movement or process conforming to a regular or periodic pattern often detectable by some corresponding indication; such as, a sound or beat, temperature, or electrical variation, etc.
2. Pertaining to a method of contraception making use of the alternation of periods of fertility with infertility in the menstrual cycle.
3. The arrangement of spoken words alternating stressed and unstressed elements.
4. An interval during which a recurring sequence of events occurs.
5. A measured movement; the recurrence of an action or function at regular intervals. 6. Movement or variation characterized by the regular recurrence or alternation of different quantities or conditions.

A rapid ventricular rhythm, approximately 60 to 110 beats per minute: Accelerated idioventricular rhythm usually results from premature beats or an escape rhythm generated by the slowing of the sinus pacemaker or acceleration of a ventricular pacemaker.

1. A pattern of slow brain waves (alpha waves) in normal people at rest with closed eyes, thought by some to be associated with an alert but daydreaming mind.
2. The normal brainwave in the electroencephalogram of a person who is awake but relaxed.
3. A pattern of smooth, regular electrical oscillations in the human brain that occur when a person is awake and relaxed.

As recorded by the electroencephalograph, alpha waves have a frequency of 8 to 13 hertz.

In electroencephalography, rhythmic oscillations in electric potential occurring at an average rate of 10 per second.

1. A pattern of electrical waves in the brain of someone who is awake and active.
2. In electroencephalography, a rapid rhythm usually of low voltage, which can be recorded in the motor areas of the brain and sometimes in the frontal regions; especially, during states of stress or anxiety or after the administration of certain drugs such as barbiturates.
3. The second most common waveform occurring in electroencephalograms of the adult brain, characteristically having a frequency from 13 to 30 cycles per second.

It is associated with an alert waking state but can also occur as a sign of anxiety or apprehension.

The study of the effect of time on biological events, especially repetitive or cyclic phenomena in individuals.

The regular recurrence, in cycles of about 24 hours, of biological processes or activities; such as, sensitivity to drugs and stimuli, hormone secretion, sleeping, feeding, etc.

This rhythm seems to be set by a "biological clock" which seems to be set by recurring daylight and darkness.

A pattern of slow brain waves, having a frequency of less than six cycles per second as recorded by an electroencephalograph, associated with deep sleep.

The pattern of slow waves (delta waves) of an electroencephalogram, having a frequency of less than 3.5 per second, and typically occurring during deep sleep, in infancy, and in serious brain disorders.

An innate internal activity cycle of an organism that appears to be initially mediated by such exogenous factors as the length of day and season but that persists in the absence of external stimuli.

An activity response to a rhythmic external environmental stimulus; such as, a photoperiodic response by an organism to the length of the day.

The rhythm of heart sounds which resembles that in the fetus in that both sounds are similar in character and intensity.

A heart rhythm produced when a pacemaker has been inserted in the atrioventricular node.

1. A pattern of brain waves having a regular frequency of 4 to 7 cycles per second as recorded by an electroencephalograph, observed during various states of light sleep or arousal.

It occurs naturally in children up to about 12 years of age, but it is considered abnormal in adults.

2. The normal brainwave in the encephalogram of a person who is awake but relaxed and drowsy.

It occurs with low frequency and low amplitude.

3. A relatively high amplitude brain wave pattern between approximately 4 and 9 hertz that is characteristic; especially, of the hippocampus but occurs in many regions of the brain including the cortex.