To matriculate is to officially start at a university: your name goes on the list, and you become a real student there, not just someone who hopes to go. In the United States people also use it for starting at a school or college, but even there enroll is the everyday word. Matriculate sounds more formal, a little British, a little like a ceremony. At some old universities there is still a matriculation day — a gown, a book to sign, and after that you belong. In most places there is no theatre; you fill in forms and pay, and that is it. Same idea. Though actually, this is not graduating. Graduating is when you finish. Matriculating is when you begin. People mix those up because both feel like a big school moment. There is also an old adjective, matriculate, meaning already on the list as a student; you can ignore it. In South Africa and some other places people say matric for the exam at the end of high school. That is a cousin use of a related word, not this verb, but you will hear it and it can throw you. And it has nothing to do with the film The Matrix, even though the letters look similar at the start.

註冊入學；取得學籍。台灣校園口語多半只說「註冊」。