A person's job is their role in society. A job is an activity, often regular and performed in exchange for payment. Many people have multiple jobs (e.g., parent, homemaker, and employee). A person can begin a job by becoming an employee, volunteering, starting a business, or becoming a parent. The duration of a job may range from an hour (e.g., odd jobs) to a lifetime (e.g.,judges).
An 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.