Professor Septima Vector is the witch who serves as the Professor of Arithmancy at Hogwarts School of Witchcraft and Wizardry during Harry Potter's time at the school. A character mentioned only by name and reputation, she is known for teaching a highly complex and demanding magical discipline. Her most notable student is Hermione Granger, who excels in the subject. Professor Vector represents the academic rigor present at Hogwarts, particularly in magical fields that require intellectual dedication over practical spell-casting.
Professor Vector's life before or after her tenure at Hogwarts is not detailed in the novels. Her presence in the story is established during the 1993-1994 school year, when Hermione Granger begins taking Arithmancy in her third year. The subject is immediately established as highly difficult, requiring the use of complicated number charts. She continues to teach Hermione through her O.W.L. and N.E.W.T. years. By the 1996-1997 school year, Professor Vector is known for assigning a significant amount of challenging homework, as Hermione complains that a “nit-picky” essay for Arithmancy is preventing her from helping Ron Weasley with his own assignments. Professor Vector's presence at the school during the Battle of Hogwarts is unconfirmed, though it is likely she participated in the school's defence alongside her colleagues.
Professor Vector's physical appearance is never described in the seven canonical novels. Based on the nature of her subject and her students' reactions, her personality can be inferred. She is presumed to be highly intelligent, logical, and methodical. The complexity of Arithmancy suggests she is a very demanding and strict teacher who holds her students to a high academic standard. Her reputation for assigning “nit-picky” essays and copious amounts of difficult homework reinforces this perception.
No specific possessions of Professor Vector are mentioned in the books, although she would have certainly owned a wand.
Professor Vector's primary relationship detailed in the series is with her student, Hermione Granger. Hermione is one of the few students shown to have both the aptitude and the interest for Arithmancy, and she continues the subject to the N.E.W.T. level. While no direct conversations are recorded, Hermione's dedication implies a level of academic respect for her professor. Her relationship with other students, such as Harry Potter and Ron Weasley, is non-existent, as they found the subject baffling and opted not to take it.