"A hard work."
Translation:O muncă grea.
Native speaker, who is more fluent in English than most of my fellow Americans, says this translates more into the sense of "It's hard work." Native English speakers would not use "a hard work," which is the literal translation.
In natural English work is not a noun it is an adjective of which "job" is the corresponding noun.
Similarly in one of your other questions you used the English sentence "I have a very hard work". No, you don't, you have a very hard JOB at which you work very hard.
I hope that makes sense.
To make matters more confusing we might say "at work" (where it is used as a noun, sorry!) and "jobbing", meaning working. Job is a smaller thing than work. Work is a very broad spectrum which may consist of many jobs! At any rate you do not have "a work". You just don't.