While grammar and usage are two terms that are linked together, they do not mean exactly the same thing. As mentioned earlier, grammar is the set of rules that governs the way language is put together into words and combined into sentences. Usage refers to the customary way language is used in a sentence. Together, the rules of grammar and usage govern the way language is expressed in standard spoken and written English.

To write effectively, students must demonstrate the ability to write clearly and correctly in standard English. In the University of Maryland system, serious wording and sentence problems that "damage the readability" or "grammar, spelling, or format problems [that] create frequent obstacles to understanding" result in an unsatisfactory essay ("Cross Curricular Initiatives; Effective Writing"). To avoid these problems, students must be aware of the rules in the following areas of grammar and usage: