Longman Dictionary of Contemporary English - reminder

~ n 1 something that makes you notice something or understand it better + of  (a reminder of the dangers of drinking and driving) + abou  (Kids need constant reminders about crossing roads safely.) be a reminder that  (Occasional bursts of gunfire are a reminder that the battle isn't over yet. | serve as a reminder (=be a reminder))  (The President's bodyguards serve as a reminder that he's no ordinary guy out for a walk.) 2 something that reminds you of something that happened or existed in the past + of  (Her disability remains as a perpetual reminder of the war years.) 3 something, for example a letter, that reminds you to do something which you might have forgotten