Private enrolment refers to pupils or students enrolled at a given level of education in institutions that are not operated by a public authority but controlled and managed, whether for profit or not, by a private body, such as a non-governmental organisation, religious body, special interest group, foundation or business enterprise.

Gross tertiary graduation ratio (only applicable for first degrees) is the total number of graduates in tertiary International Standard Classification of Education (ISCED) 5A programmes expressed as a percentage of the total population of the age at which students theoretically finish their first degree programme, in a given country

GER is the ratio of total enrolment, regardless of age, to the population of the age group that corresponds to the same level of education. GER can exceed 100% due to the inclusion of over-aged and under-aged students, because of early or late school entrance, and grade repetition. For the tertiary level, the population used is the 5-year age group starting from the official secondary school graduation age (Source: UIS, Education Indicators - Technical Guidelines: p.9)

Marginalised groups are all those excluded from governmental policy and access to education including: women and girls, indigenous peoples and minorities, persons with disabilities, persons with HIV / AIDS, child labourers, persons in detention, migrants, refugees and IDPs, and persons living in poverty (Source: Audrey Chapman (2007) Development of Indicators for Economic, Social and Cultural Rights: The Rights to Education, Participation in Cultural Life and Access to the Benefits of Science: p.145)

Percentage of students at the lowest level of science proficiency is the percentage of students at the lowest level of proficiency on the science scale in national or international assessments

Percentage of students at the lowest level of mathematics proficiency is the percentage of students at the lowest level of proficiency on the mathematics scale in national or international assessments

Percentage of students at the lowest level of reading proficiency is the percentage of students at the lowest level of proficiency on the reading scale in national or international assessments

Mean performance on the mathematics scale is the mean mathematics score for students in national or international assessments

Mean performance on the science scale is the mean science score for students in national or international assessments

Mean performance on the reading scale is the mean reading score for students in national or international assessments