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Why do I keep forgetting new words in a language?

Benedict Grima · Last updated 8 October 2026

Why do I keep forgetting new words in a language? No matter how different the foreign language, you usually forget a word because you have seen it too few times, and at the wrong moments, for your memory to hold on to it.

A new word fades fastest in the first day or so. You remember a new word when a) you pull it back out of memory at intervals that slowly grow longer, b) it is tied to something real in your life, and c) you keep running into it.

English people tell themselves they are untalented at learning foreign languages. This is not true! We just lack the need, motivation and exposure to learn. Almost half the world’s population speaks more than one language,¹ so it’s well within your grasp to learn a foreign language. If you keep forgetting vocabulary, it doesn’t mean you are bad at languages. It happens to everyone, including people who speak 5 or more!

My reason

I find the Polish language a challenge because Polish vocabulary is mostly very different to English. When a situation comes up which requires a particular word, as a beginner I’ll ask my wife, a native speaker, for the translation. Particularly when we’re in Poland together, as the immersion makes learning feel urgent. She taught me the word for hungry, głodny, and I immediately knew this was going to be hard to remember. I repeated the word a few times, and asked for the spelling to picture the word. However, within a few hours my mother-in-law was offering me dinner and I wanted to explain that I wasn’t hungry. I had eaten on the journey there, and all I could remember was that the word for “hungry” began with a “g”.

A method for aiding memory, which I used here and which we use in the Lumessa app, is to devise a “memory hook”: a story or association you make to connect new, hard-to-remember information to something familiar so your brain can recall it easily. Here I considered that głodny is similar to “greedy”, which is conceptually close to “hungry”. Here’s my trick for remembering that Polish word!

Compare my troubles recalling głodny with effortlessly remembering kawa (coffee). I have never had to try to remember kawa. Every morning in Poland, I come downstairs to the kitchen and within seconds my wife or one of her sisters is graciously offering me kawa. I didn’t learn it from a list. I learnt it by hearing it, asking for it and drinking it, day after day.

In my opinion, the difference between those two words is most of the answer to this question.

Is it normal to forget new words so quickly?

Yes. In the 1880s the German psychologist Hermann Ebbinghaus spent months learning lists of nonsense syllables and testing himself on how much he had kept. What he found became known as the forgetting curve: memory retention drops steeply in the first few hours after learning, then levels off.

In 2015 the researchers Jaap Murre and Joeri Dros repeated his experiment with a single volunteer and got a very similar result.² The steepest loss came within the first hour and the first day.

A word of caution, though. Ebbinghaus was learning meaningless syllables, not words in a real language that you want to use with real people, and both studies tested one person. The curve shows the general shape of forgetting. It is not a timetable for how long herbata (tea) will last in your head.

Still, the shape of the forgetting curve explains a lot. If you learn 10 words on Sunday and don’t see them again until the following Sunday, most of them will have gone. That is simply how memory behaves.

How many times do you need to see a word before you remember it?

More than most people expect. The linguist Stuart Webb gave Japanese students of English some reading passages in which certain words had been replaced with imaginary ones, so that every student was seeing them for the first time.³ Each imaginary word appeared once, three times, seven times or ten times.

Every increase brought more knowledge of the word, and after ten encounters the gains were sizeable. Even so, Webb concluded that 10 exposures may not be enough to know a word fully: its spelling, its grammar, the words it tends to appear with.

This is why the words you meet in everyday life are the easiest ones to learn, as I wrote in How to learn Polish to talk to your partner’s family. They come back to you on their own, because you keep encountering them through lived experience. A word on a list only comes back if you bring it back.

Why does rereading a word not help it stay?

Because recognising a word and recalling it are different skills. When you read that marchewka means “carrot” for the fifth time, it feels familiar, and familiar feels like learning. But a conversation will ask you to produce marchewka from nothing, with no English beside it.

The psychologists Jeffrey Karpicke and Henry Roediger tested this with students learning 40 Swahili–English word pairs.⁴ Once a student had recalled a pair correctly, the pair was either kept in the tests or dropped from them. A week later, the students who had kept testing themselves recalled about 80% of the pairs. Those who kept studying the pairs but were no longer tested on them recalled only about a third.

What I find most telling is that the students couldn’t feel the difference. Every group predicted they would remember about half the words.

So the practical lesson is simple: cover the translation, and try to say the word before you check. Exercise the recall: it’s the magic to learning properly.

When should you review a new word?

Just as you are starting to forget it, and then at longer and longer intervals.

A large review of the research, covering more than 300 experiments on remembering words and facts, found that spreading practice out beats cramming it into one sitting.⁵ But that raises an obvious question: how far apart should the reviews be? It’s tempting to think the answer is “as far apart as possible”. It isn’t.

The way I think of it is this. If you review głodny an hour after learning it, the word is still sitting in your head. Recalling it takes no effort, so the review does very little. If you wait two months, the word has gone completely. There is nothing left to recall, so you are not really reviewing at all: you are learning it again from scratch. Somewhere between those two is the gap that helps most: long enough that you have to work to find the word, and short enough that you can still find it.

In 2008 the same team of researchers tested this directly.⁶ More than 1,350 people learned a set of facts. They reviewed them after a gap of anything up to three and a half months, and were then tested up to a year later. Whatever the test date, the pattern was the same: making the gap longer helped at first, then reached a peak, and after that it started to hurt. That peak is the best interval.

The second finding matters most for learning a language. The best interval depended on how long you wanted to remember. For a test one week later, the best gap was about 20 to 40% of that week, so a review after roughly one and a half to three days. For a test one year later, it was about 5 to 10% of the year, so a review after roughly two and a half to five weeks.

In other words, the longer you want to remember something, the longer the best gap between reviews. But it is never so long that the word has already gone.

A word of caution, though. These were facts, not words in a foreign language, and each person had a single review, not a series. The step from there to “keep stretching the gaps, one review after another” is my own reading, not something this study tested.

This is why the Lumessa app brings a new word back for review the next day, then after three days, a week and three weeks, and after that every two or three months. If you get it wrong, the word starts again from the next day.

Why do some words stick and others don’t?

In my experience, three things make the difference.

Meaning

Words tied to a moment, a person or a place stay. I remember grzyb (mushroom) because I learnt it mushroom-picking in the forest with my wife’s grandparents. A word from a vocabulary list has nothing to hold on to in your mind, which is why I suggest learning words from your own life first: your family, your kitchen, your journey to work.

Sound

A word you can’t pronounce is much harder to retain. Polish szczęście (happiness, or luck) looks like a jumble of consonants until you can say it. Once you can, it becomes a word, and you have a sound to remember as well as a spelling. That is why I always start to learn a language by focusing carefully on its alphabet and pronunciation.

Similar words

Words that look or sound alike are easily confused. You learn one, then its lookalike arrives and the two blur together. I wrote about this in Can you learn Spanish and Italian at the same time?, where burro means “donkey” in Spanish and “butter” in Italian. When two words keep swapping places in your head, learn them on different days, and give each one its own picture.

Does making up your own memory trick help?

Often, yes. In 1978 Norman Slamecka and Peter Graf found that people remembered words better when they had to come up with the word themselves, from a clue, than when they simply read it.⁷ This became known as the generation effect.

I should be clear about the evidence here. Their experiments used English words, produced from clues such as a synonym and a first letter. They did not test memory tricks for foreign words. The step from their finding to “invent your own memory tricks” is mine, and it comes from experience rather than a study.

This is where my “greedy” memory hook came in handy for remembering that the Polish głodny means “hungry”.

Consider that a good memory hook only has to last perhaps a few weeks. Once you have recalled the word enough times, you stop needing it, and the word simply comes to you.

How do I remember new words?

If you want to start this week, here are 5 things I would do:

1. Learn fewer words and see them more often. I would rather learn 5 words properly than have seen 20 one time each.
2. Test yourself before you check. Cover the English and say the word. If you can’t, look, then try again later that day.
3. Space it out. Come back to a word the next day, then a few days later, then a week later.
4. Start with the words of your own life: your family, your food, your street.
5. Say every word out loud. Hearing yourself say it gives your memory one more thing to hold on to.

Forgetting is part of learning

Everyone forgets new words. What makes the difference is quality reps: going back for them again and again. Each time you reach in your head for a word that is starting to fade, and find it, it tends to last longer before it fades again.

Between reviews, it also helps to be able to see the words you are learning. That is why we built a lock screen widget into the Lumessa app: it shows the word you are learning on your phone throughout the day, so you run into it the way I run into kawa in a Polish kitchen.

See how Lumessa works