A child means every human being below the age of eighteen years unless, under the law applicable to the child, majority is attained earlier. See article 1, Convention on the Rights of the Child (CRC).

A child population is a particular group of children, such as ‘all children in detention on a particular date’, that must be counted in order to measure a particular indicator.

The competent authority is the part of the juvenile justice or adult criminal justice system that is responsible for making procedural or disposition decisions regarding a child’s case.

A complaints mechanism is any system that allows a child deprived of liberty to bring any aspect of the treatment that child has received, including violations of his or her rights, to the attention of the authority responsible for the place of detention, or any other official body established for such purpose.

A child is in conflict with the law when he or she has committed or has been accused of having committed an offence. Depending upon the local context, children may also be in conflict with the law when they are dealt with by the juvenile justice or adult criminal justice system for reason of being considered to be in danger by virtue of their behaviour or the environment in which they live.

A child is convicted where he or she is found guilty of having committed an offence by the decision of a competent authority.

Means widespread consistent norms in the state in question, including long standing tribal or indigenous rules that may be known by a large part of the population.