A man-year is a measure of work: what one person does in a year of working time — usually a full-time working year, not every hour a person is alive. Big projects use it. “This will take three man-years” might mean three people for one year, or one person for three years. It is the same kind of measuring word as man-hour, just a bigger unit. Though actually, some people now say person-year, for the same reason they say person-hour: man was meant as “human,” but it sounds male. It is office and engineering language, not everyday talk.

人年（用一個人做一年的工作量來估專案）。