Lecturer is an academic rank within many universities, though the meaning of the term varies somewhat from country to country. It generally denotes an academic expert who is hired to teach on a full- or part-time basis. They may also conduct research.
Iranian lecturer sample 2014.jpg
An Iranian associated professor, teaching C language programming
Mathematics lecture at the Helsinki University of Technology.jpg
A mathematics lecture, apparently about linear algebra (calculation of eigenvalues and eigenvectors)...