Is work a singular or plural word?

We are often confused by the common-used word 'work' whether it is singular or plural, especially in written English.

Well, in many occasions it is a uncountable word.For example,when it means as  

      (1) the job that a person does especially in order to earn money: He started work as a security guard.
      (2) the duties that you have and the activities that you do as part of your job: The accountant described his work to the sales staff.
      (3) tasks that need to be done: Taking care of a baby is hard work.
      (4) materials needed or used for doing work, especially books, papers, etc: His work was spread all over the floor.
      (5) the place where you do your job: I have to leave work early today.
      (6) the use of physical strength or mental power in order to do or make something: We started work on the project in 2009.
      (7) a thing or things that are produced as a result of work: Is this all your own work 
      (8) the result of an action; what is done by somebody:The damage is clearly the work of vandals.

However, when it means as follows, work can be used as a countable word.

      (1) a book, piece of music, painting, etc: Beethoven's piano works
      (2) (often in compoundsactivities involving building or repairing something: They expanded the shipyards and started engineering works.
      (3) (often in compoundsa place where things are made or industrial processes take place: Raw materials were carried to the works by barge./ a brickworks