Work and job as nouns and verbs Work is both a verb and a noun (uncountable); job is mostly used as a noun (countable): I’m busy – I have a lot of work. (uncountable noun) I have a lot of works. I have two jobs – I’m a taxi driver, but I also work as a part-time fireman. (countable noun) I’m a teacher at a nursery. It’s a great job – I love it. (countable noun) We say go to work, start work, finish work: I start work at 8 o’clock every morning. I start my job at 8 o’clock every morning. I go to work by bus. I travel to my job by bus. Source: http://speakspeak.com/confusing-words/job-work-difference

A short answer is that "job" is countable and "work" is uncountable.

There is a substantive difference in meaning between the two words. please see this illustration: I have a job at XYZ Company. I don't have to do any work there; I just need to look pretty every day.