A person employed in an official capacity for the purpose of guiding and directing the learning experience of pupils and students in an educational institution, whether public or private. Usually, the person should have completed a professional training course in a teacher education institution leading to the award of appropriate credentials.
Source: UNESCO 1984, Global

An individual with pedagogical and professional skills, as well as experience, who teaches students.
Source: ILO 2006, Global

A person whose function is to impart knowledge, know-how or skills to learners in an education or training institution.
Source: CEDEFOP 2008, Europe

Persons employed full-time or part-time in an official capacity to guide and direct the learning experience of pupils and students, irrespective of their qualifications or the delivery mechanism, i.e. face-to-face and/or at a distance. This definition excludes educational personnel who have no active teaching duties (e.g. headmasters, headmistresses or principals who do not teach) or who work occasionally or in a voluntary capacity in educational institutions.
Source: UNESCO UIS 2013, Global

Persons who, through their duties, are involved directly in the education process in the Member States.
Source: EU Commission LLP 2007-2013, Europe