Your application will be read by the faculty members in the department or program to which you are applying. (Undergraduate admissions, in contrast, relies on administrators who focus on admissions across the entire college or university.) Scholars in the field will evaluate your preparation and potential for the pursuit of a degree in their discipline. What’s more, you are generally writing for an even narrower audience: Those faculty members who are scholars in your area of interest. Thus, describing a desire to study electrical engineering or educational psychology is not specific enough. The department needs to match you with an advisor. What you want to research as a student must fit with the expertise of at least one faculty member in the department. 

Thus, even before you begin writing your statement of purpose, you need to research the department to which you are applying. Read bios on the university website, paying special attention to the exact wording of someone’s research interests (this will help you shape your own language about the field), then drill down to peruse the titles of a professor’s most recent publications. Pay special attention to the research interests that faculty members list in their bios. If CVs are posted (the curriculum vita is a scholarly resume), skim through those as well. Reading through bios and CVs as well as reading recent publications will help guide you in describing your scholarly interests. Don’t copy and paste or repeat verbatim (plagiarism is a deadly sin in academia) but tweak the wording to demonstrate that you know and understand your discipline and proposed specialty.

If you don’t find faculty members working on topics that interest you for your own research, then rethink your application to that particular program. If you don’t see a fit, the faculty won’t either. Note, however, that even as you seek to identify the one or two faculty members you could imagine as your advisors, you need to know what others in the department do as well. Remember, you’ll be taking classes with and interacting with lots of professors across a variety of specialties. Again, you want everyone to think that you will be a valuable presence in seminars, colloquia, and other department events.

Duke University gives an excellent example of how to target a specific audience, referencing the field of English Literature. Here are four sample sentences. Which is strongest?

1. I am particularly interested in studying the history of the Victorian novel at Hotshot University.
2. I am particularly interested in studying the history of the Victorian novel with Professor Fascinating at Hotshot University.
3. Professor Fascinating’s work on Dickens and Eliot is of particular interest to me. 
4. I am particularly interested in how Professor Fascinating’s study of Dickens and Eliot challenges prevailing assumptions about the relationship between gender and narrative form in Victorian literature.

The fourth sentence is much stronger than the others, revealing an awareness of the scholarship in the field and the contributions of a faculty member in the target program.