* Undergraduate: This refers to a student who is pursuing a bachelor's degree (e.g., BA, BSc, BEng). It's the first stage of higher education after secondary school (high school). Undergraduates are typically completing their initial degree program.
* Graduate: This term is broader and encompasses anyone who has already earned a bachelor's degree. It includes both those currently pursuing a postgraduate degree (see below) and those who have completed their postgraduate studies and hold a master's degree, doctoral degree, or other advanced degree. Essentially, "graduate" simply means "having graduated" from a bachelor's program.
* Postgraduate: This refers to a student who is pursuing a degree *after* having already completed a bachelor's degree. This includes master's degrees (MA, MSc, MEng), doctoral degrees (PhD, EdD), and other advanced professional degrees (e.g., MBA, LLM, MD). Postgraduate studies represent advanced study beyond the undergraduate level.
In short: All postgraduates are graduates, but not all graduates are postgraduates. Undergraduate is a distinct stage prior to both graduate and postgraduate status.