The definition of alas is to express unhappiness, sorrow or regret.interjection
An example of alas is someone saying they wish they'd known about an event before rsvp'ing for another, such as "Alas, I wish I would have known about the event because I have already agreed to go somewhere else."YourDictionary definition and usage example. Copyright © 2013 by LoveToKnow Corp.
Origin: ME < OFr a las, helas < a-, he-, ah + las, wretched < L lassus, weary
Used by arrangement with John Wiley & Sons, Inc.
Origin: Middle English, from Old French a las, helas, ah (I am) miserable, from Latin lassus, weary; see lē- in Indo-European roots.