In all your professional writing, you need to convey not only your intended message but also that you are indeed a professional. No matter if you are writing a research manuscript, a grant application, a journal cover letter, a job application letter, an academic essay, or a work email, you you need to sound like a knowledgeable writer, an effective communicator, and a professional in your field. Your text has to be easy to read and understand, while not annoying or offending the reader in any way. Especially if there is a limit on the number of words allowed (eg, in journal manuscripts), you need to concisely say what you mean, mean what you say, and not be mean in what you say.
