Take the noun tenure for the period of time a person holds a position or office. Your tenure as a student ends when you graduate high school — unless, of course, you go on to college.
Tenure from the Latin tenere means "to hold" and refers to the period of time a person works at a particular job or in an office. A president might have to deal with a recession during his tenure in the White House. In university jargon, if you have tenure, you have a permanent teaching position or professorship. In this sense, tenure can also be used as a verb. You've got it made if you're tenured at age 29.