Teachers and sometimes entire academic departments or institutions create the requirements for expository essays. Expository essays are academic and, when successfully achieved, conform to a set of academic guidelines. These guidelines can be very specific, such as following a particular documentation style such as MLA (Modern Language Association), APA (American Psychiatric Association) or Chicago style, or a predetermined format, such as the five paragraph essay.
Overall, expository essays include mature vocabulary, proper grammar, a defined thesis, smooth transitions and cited evidence from scholarly publications. These essays should avoid emotional expression and pronouns such as "I," "you" or "we." Expository writing is straightforward and factual with an objective "voice of an expert" feel to the writing.
In contrast, business communication rarely presents just facts but presents facts in relation to a goal, mission statement or circumstance particular to a specific business function. Thus, the business task plays a large role in determining the style of the business communication. Emotion, subjective observations as well as the use of "I," "we" or "you" are common in business communications.
In expository essays, the purpose is to create work that an academic instructor will assess positively through good grads, comments, personal recommendations or the chance for specialized instruction. Business communication, on the other hand, is far more broad in writing tasks, intended audience and purpose.
Business communication may be formal, such as official presentations, memos and proposals, or informal, such as an email or jotting notes. Business communication is diverse in style and substance, depending on the task and the position of the reader and of the writer. A quick note to a close colleague will sound and read far different than a formal proposal to a superior. Business communication is integral to how the business itself functions.
For expository essays, the audience is academic---a teacher or professor. For business communication, the audience may be a colleague, a subordinate, a superior, a client or any number of individuals or groups involved with the running of a business. In other words, expository writing is usually for one audience, but business communication may potentially have several audiences---anyone and everyone working for a business as well as anyone and everyone with whom a specific business interacts.