I've worked here all of my 'adult life'. [=I've worked here since I became an adult]
People who are close friends as children aren't always friends as 'adults'.
The university offers a popular program of 'adult education'.
(..) They, better than I, know what's best for you. Don't let me see you in here again. Now, Margaret Sadovsky. I think some adult guidance, supervision... could benefit you too, young lady. Because you have no legal guardian-- Is that right? (..)1996 Foxfire