깜빡하다, 까먹다, 이저어버리다… All three of these words are translated as “to forget” in English, but they have slight differences. Using one in the wrong situation could sound awkward or just flat-out wrong! Let’s take a closer look at these words and see how they differ.
깜빡하다 is not the most polite of words, so you can use it with your friends but not your boss. This “forget” is a momentary or short-term forgetting. For example, have you ever picked up your phone with a specific purpose but then, in the second it took to unlock your phone, forgotten what exactly you needed to do? Of course you remember after a minute of staring at your home screen… that’s 깜빡하다! Or maybe your friend asks if you brought them the book you told them yesterday that you would return today… but oops, you forgot to grab it on your way out. 깜빡했다! Things that you forget with 깜빡하다 are not things that are very important; for example, you wouldn’t use it when talking about how you forgot about a big exam or how you forgot some important documentation you needed.
까먹다 is also not a very polite word, so again, don’t go telling your boss that you 까먹었다’d that important file they asked for! Compared to 깜빡하다, 까먹다 can cover things a bit more long-term and a little more important, but still not final exam or important documentation-type important (you miiiight be able to get away with using 까먹다 for that, but 잊어버리다 would be more appropriate). Let’s say your friend calls you a bit angry because they’re waiting for you to show up… to a planned hangout session that totally slipped your mind. This is the sort of thing that 까먹다 covers!
잊어버리다 can be used in polite situations and can be used for forgetting something entirely or forgetting something for a period of time. This is the word you use for that exam you forgot about or that paperwork you should have turned in three days back. It feels a bit more final than the above two words, though you can use it for those two meanings when in polite company (or if you just forget those words!) with no negative repercussions.
Hope this helped! Happy studying~