A job is an activity, often regular, and often performed in exchange for payment. A person usually begins a job by becoming an employee, volunteering, or starting a business. The duration of a job may range from an hour (in the case of odd jobs) to a lifetime (in the case of some judges). The activity that requires a person's mental or physical effort is work (as in "a day's work"). If a person is trained for a certain type of job, they may have a profession. The series of jobs a person holds in their life is their career.