This definition allows for certain kinds of unemployment, where the number of unemployed workers equals the number of vacancies. Unemployment of this kind can take two forms: frictional and structural. Frictional unemployment is where the unemployed are searching for the best possible jobs whilst employers are also searching for the best possible employees to fulfil those jobs. Structural unemployment exists when the skills and geographical locations of the unemployed workers do not correspond to the skill requirements and locations of the vacancies. In either case, there exists a job for every worker, and a worker for every job.