The UNHCR (2004) defines unaccompanied minors as children below the age of 18 who ‘have been separated from both parents and are not being cared for by an adult, including a distant relative, who, by law of custom, is responsible to do so’. From the point of view of statistics, migrant minors and adolescents below the age of 18 represent almost half of the worldwide refugee population, making up an estimated one-third of the total world population, the majority of them being unaccompanied (for example, UNHCR, 2012, 2013; Vervliet et al, 2015, p 468). On the other hand, the term ‘separated’ refers to children under the age of 18 who are similarly separated from both parents or from their previous legal or customary primary caregiver, albeit usually living with extended family members, such as siblings, or an uncle or aunt (UN General Assembly, 2001, p 3).

Adding to UNHCR's definition, the European Council, under Art. 2(e) of Directive 2013/ 33/ EU, provides a more detailed description of the term. More specifically, according to the latter, an unaccompanied child is:

However, despite the implementation of the definition in the Greek legal framework, it was never clarified in the national context how migrant children may end up unaccompanied after they enter the country.

On this matter, practice confirms that migrant minors usually leave their countries of origin alone but join other individuals in the process, often relatives already en route to safe destinations. Alternatively, children may embark upon this journey alongside close relatives or primary caregivers, but eventually end up alone. For this reason, it has been supported that the term ‘separated’ may be considered more accurate, as the term ‘unaccompanied’ veils ‘the presence of many social actors who shape these migrations at the onset, during the journey, and at the destination’ (for example Kohli, 2007, p 4; Menjívar and Perreira, 2019, p 201).

With regard to their background, unaccompanied children most commonly originate from areas that are severely affected by armed conflicts, warfare activities and a rather unstable socio-political regime overall.