Table 1.

Glossary

Amplitude	The maximum variation measured from mean
Acrophase	Phase angle corresponding to the peak value of the rhythm
Biological (peripheral) clock	Self-sustained circadian oscillation in absence of external periodic input
Central (master) clock	The suprachiasmatic nucleus located in the basal hypothalamus of the brain, receiving external information via the retina
Chronobiology	Study that examines timing processes or biological rhythms
Chronotype	The propensity for the individual to sleep at a particular time during a 24-hour period; it can be broadly categorised into three groups: (1) morning-type (wake up early and sleep early, peak of physical and mental activity during early part of the day); (2) evening-type (wake up late and sleep late, with peak physical and mental activity during end part of the day) and (3) neither
Chronotherapy	Synchronisation of drug concentration to rhythms in disease activity
Circadian rhythm	Biological processes that display oscillation over 24-hour periodicity
Diurnal variation	Variation during the day between dawn and dusk