JOB:
A job is a regular and official activity that you do, and receive money for. It is also called a profession or an occupation. It can be full-time or part-time
- She has a great job
- Being a doctor is a very demanding job
-This is the best job I have ever had
- I love this job even though it is part- time
WORK:
The word work is more general than "job" - whereas "job" is a specific occupation, "work" refers to general efforts and activities done to accomplish a goal.
- I won´t be able to go as I have a lot of work
- Don´t speak to me while I am at work (or workplace)
- They have been looking for work since the factory closed
CAREER:
The career is the total progression of one´s professional life. It can include many different jobs over the years.
- He had a short career as a teacher
- She sought a career as an engineer
- If she studies for two extra years she will have a better career prospect