In most of its meanings, work is an uncountable noun, and so:
▪ it rarely comes after a or a number
▪ it is rarely used in the plural
✗ It is very common for university students to get a part-time work.
✓ It is very common for university students to get part-time work.
✗ They want to relax after the pressure of their works.
✓ They want to relax after the pressure of their work.
Q: What is the difference between work and job?
A: Work refers in general to things people do to earn money. Job is used when you are referring to the particular thing that someone does regularly in order to earn money:
Mr Biswas goes to Port of Spain to look for work. By chance he gets a job on a newspaper.
Work can be a countable noun when it means ‘something produced by a writer, painter, musician, or other artist’:
Copying from the works of the Great Masters was one of a young art student’s most important tasks.
This opera is indeed a work of great dramatic intensity.