Understanding Word Count
Word count is a metric used by publishers and editors. In fact, you will usually get a writing assignment with only two parameters: the topic and the word count.
Most of the time, of course, the target reader is implied because writers and publishers usually cater to a certain reading public. The deadline is also fixed for periodicals and probably for books as well because publishers usually have a target number of titles planned for their publishing calendar.
Interestingly, we can gauge a writer’s writing skill by how much he can produce in a given period of time (i.e., word count within a given number of calendar days). It’s a metric every writer should be aware of because it’s the language every editor and publisher speaks.
Anybody Can Write a Book 