Chronotype
Describes whether your body is more alert in the morning or in the evening. Some people get up early, some are night owls.
A little more detail
The time of day at which a person tends to place sleep and wakefulness within the 24-hour day, determined largely by the circadian clock. In a population, sleep and wake times are almost normally distributed; extreme morning types are getting up when extreme evening types have just fallen asleep. It is measured with the Horne Östberg morningness eveningness questionnaire (MEQ) and the Munich Chronotype Questionnaire (MCTQ); the MCTQ uses sleep timing on both work and free days. Chronotype changes with age and sex.
Source: Roenneberg T, Kuehnle T, Juda M et al. Epidemiology of the human circadian clock. Sleep Med Rev. 2007;11(6):429-438. doi:10.1016/j.smrv.2007.07.005