What we measured
We analysed 35,604 Korean flashcard reviews from 761 learners across 804 cards. The cards came from curated frequency decks and words saved from conversations. Reviews used a 4-point scale: Again (1), Hard (2), Good (3) and Easy (4), scheduled by an FSRS spaced-repetition scheduler.
An Again rating means the learner failed to recall the card. Each listed card had at least 30 reviews from at least 20 learners.
We also counted word lookups, which our analytics record when a learner taps a word in the transcript of a live conversation. That dataset contains 6,019 lookups by 700 learners across 1,764 distinct words over the 180 days to 9 September 2026. Listed lookup words were tapped by at least 10 learners.
This is data from one app's learners over the stated windows. It shows what happened on Lingrow, not what every person learning Korean will experience, and we'll update the page as more reviews come in.
The most forgotten Korean words
Abstract words and light verbs had the highest Again rates
것 led the ranking with a 65% Again rate across 1,264 reviews by 671 learners. 되다 followed at 63% across 1,126 reviews by 530 learners.
대하다 had a 62% Again rate across 721 reviews by 292 learners. 수 reached 58% across 1,053 reviews by 522 learners. 하다 and 있다 each reached 53%, across 1,190 and 1,063 reviews respectively.
That puts the abstract grammar words and light verbs well above concrete nouns. 생각 had a 4% Again rate, 원 9%, 여자 9% and 집 21%. The connectives 그래서 and 그리고 (typed as adverbs in the deck) were also easier, at 8% and 26%.
Most forgotten Korean words on Lingrow
| Rank | Word | Gloss | Type | Reviews | Learners | Again rate | Good rate |
|---|---|---|---|---|---|---|---|
| 1 | 것 | thing; something | bound noun | 1,264 | 671 | 65% | 35% |
| 2 | 되다 | to become; to be | verb | 1,126 | 530 | 63% | 37% |
| 3 | 떠나다 | to leave; to depart | verb | 131 | 37 | 62% | 38% |
| 4 | 대하다 | face; confront; handle; deal with | verb | 721 | 292 | 62% | 38% |
| 5 | 등 | back; top | noun | 821 | 386 | 59% | 41% |
| 6 | 수 | number; figure | noun | 1,053 | 522 | 58% | 42% |
| 7 | 주다 | give; assign | verb | 740 | 335 | 58% | 42% |
| 8 | 같다 | to be the same; to be similar | adjective | 721 | 341 | 58% | 42% |
| 9 | 따르다 | follow; equal; match | verb | 193 | 52 | 57% | 42% |
| 10 | 때 | time; when | noun | 687 | 347 | 56% | 44% |
| 11 | 통하다 | flow; pass; circulate; respond | verb | 136 | 35 | 55% | 45% |
| 12 | 않다 | to not do; not | adjective | 838 | 419 | 55% | 45% |
| 13 | 위하다 | to do for the sake of | verb | 251 | 104 | 54% | 46% |
| 14 | 있다 | to be; to exist; to have | verb | 1,063 | 558 | 53% | 47% |
| 15 | 하다 | do; perform; make | verb | 1,190 | 635 | 53% | 47% |
| 16 | 거 | thing | noun | 741 | 365 | 53% | 47% |
| 17 | 들다 | to enter; to hold; to cost | verb | 106 | 29 | 51% | 49% |
| 18 | 때문 | because; reason | bound noun | 199 | 81 | 51% | 49% |
| 19 | 지나다 | pass; elapse; cross | verb | 95 | 29 | 50% | 50% |
| 20 | 그렇다 | to be so; yes | adjective | 240 | 85 | 49% | 51% |
| 21 | 안녕하다 | peaceful; calm | adjective | 262 | 120 | 49% | 51% |
| 22 | 크다 | grow; grow up; become an adult | verb | 248 | 101 | 48% | 52% |
| 23 | 보다 | see; look at; notice; watch | verb | 845 | 432 | 48% | 52% |
| 24 | 그 | he; that | pronoun | 833 | 450 | 48% | 52% |
| 25 | 사회 | society; world | noun | 170 | 57 | 48% | 52% |
| 26 | 나오다 | come out; get out; emerge; show up | verb | 169 | 76 | 47% | 53% |
| 27 | 없다 | to not exist; to not have | adjective | 853 | 458 | 47% | 53% |
| 28 | 알다 | to know; to understand | verb | 244 | 104 | 46% | 54% |
| 29 | 받다 | to receive; to get | verb | 163 | 68 | 46% | 54% |
| 30 | 그러다 | to do so; and then | verb | 116 | 33 | 46% | 54% |
The easiest Korean words to remember
Concrete words led the easiest cards
생각 had the lowest Again rate of any card that met the thresholds, at 4% across 51 reviews by 25 learners. 그래서 followed at 8% across 38 reviews by 20 learners.
원 and 여자 each had a 9% Again rate. 원 received 55 reviews from 25 learners, while 여자 received 43 reviews from 21 learners. 왜 had a 12% Again rate across 42 reviews by 21 learners.
The easiest group includes concrete nouns, a connective and a common question word. That pattern contrasts with the high Again rates recorded for 것, 되다, 수 and 대하다.
Easiest Korean words to remember
| Word | Gloss | Type | Reviews | Learners | Again rate |
|---|---|---|---|---|---|
| 생각 | thought; memory | noun | 51 | 25 | 4% |
| 그래서 | so; therefore | adverb | 38 | 20 | 8% |
| 원 | won | noun | 55 | 25 | 9% |
| 여자 | woman; feminine woman | noun | 43 | 21 | 9% |
| 왜 | why | adverb | 42 | 21 | 12% |
| 많이 | much; a lot | adverb | 58 | 31 | 16% |
| 가장 | best | adverb | 44 | 24 | 16% |
| 두 | two | determiner | 77 | 36 | 18% |
| 앞 | front; being previous | noun | 67 | 34 | 19% |
| 함께 | together; along with; coupled with | adverb | 72 | 39 | 19% |
| 먹다 | to eat; to drink | verb | 80 | 37 | 20% |
| 저 | I; me | noun | 100 | 47 | 21% |
| 집 | house; family | noun | 113 | 53 | 21% |
| 아니요 | no; no sir; no ma'am | interjection | 88 | 41 | 24% |
| 좀 | a little; please | adverb | 77 | 38 | 25% |
Recall by word type
Bound nouns and verbs were forgotten most
Bound nouns had a 59% Again rate across 1,680 reviews. Verbs followed at 51% across 9,217 reviews.
Nouns sat at 45% across 8,765 reviews. At the other end, determiners had a 30% Again rate, interjections had 32%, and adverbs had 33%.
These are reviews-weighted rates for the same set of cards. They describe how learners on Lingrow rated those cards, not an inherent difficulty score for every word in each group.
Again rate by word type
| Type | Reviews | Again rate |
|---|---|---|
| bound noun | 1,680 | 59% |
| verb | 9,217 | 51% |
| pronoun | 1,082 | 48% |
| adjective | 4,331 | 47% |
| noun | 8,765 | 45% |
| adverb | 1,693 | 33% |
| interjection | 295 | 32% |
| determiner | 636 | 30% |
Why the gloss matters
A short gloss can leave out the useful context
The back of each Lingrow card is the deck's short dictionary gloss. For a concrete word like 원 (9% Again) or 집 (21%), a one-line gloss covers most of what there is to know. For abstract grammar words, the gloss itself is part of why the card is hard.
The card for 것 says "thing; something", while 되다 says "to become; to be". 수 says "number; figure". 대하다 says "face; confront; handle; deal with".
These words mostly appear inside grammar patterns, and a short gloss can't show those patterns. 것 turns a verb phrase into a noun in -는 것 and marks the future in -ㄹ 것이다. 수 in -(으)ㄹ 수 있다 means "can", where "number" is no help at all. 되다 shows up in 안 되다 and 돼요 to say whether something is allowed, not only in "to become".
We can't say from this data that another gloss would produce a different result. What the data shows is that learners often failed to recall these cards as presented.
Keep that in mind when reading the Again rates for 것 (65%), 되다 (63%), 수 (58%) and 대하다 (62%). Those rates measure recall of the card and its gloss, not every possible use of the word.
A Korean dictionary can help learners inspect a word after meeting it in context. The sentence around the word remains important, especially when several uses share a short gloss.
What beginners look up in conversations
Greetings and common verbs produced the most lookups
Learners made 6,019 word lookups across 1,764 distinct words. The taps came from 700 learners during the 180 days to 9 September 2026.
안녕하다 led with 164 lookups by 117 learners. 오다 followed with 107 lookups by 53 learners, while 좋다 received 96 lookups by 55 learners. 저 received 95 lookups by 32 learners.
하다 received 81 lookups by 42 learners. 있다 and 주다 each received 61 lookups, from 43 and 35 learners respectively. 반갑다 had 59, 이름 had 51, and 드리다 had 47.
These are words beginners get stuck on in their first conversations. They are not a frequency list of Korean. The results are shaped by the scenarios beginners play first, including greetings, cafe and convenience store conversations.
Words beginners look up mid-conversation
| Word | Lookups | Learners |
|---|---|---|
| 안녕하다 | 164 | 117 |
| 오다 | 107 | 53 |
| 좋다 | 96 | 55 |
| 저 | 95 | 32 |
| 하다 | 81 | 42 |
| 있다 | 61 | 43 |
| 주다 | 61 | 35 |
| 반갑다 | 59 | 26 |
| 이름 | 51 | 21 |
| 드리다 | 47 | 30 |
| 어떤 | 44 | 31 |
| 뭐 | 44 | 18 |
| 말하다 | 43 | 24 |
| 돕다 | 41 | 31 |
| 좋아하다 | 40 | 21 |
| 가다 | 38 | 18 |
| 거 | 37 | 30 |
| 이다 | 37 | 21 |
| 데우다 | 37 | 22 |
| 고르다 | 35 | 29 |
| 알다 | 31 | 19 |
| 카드 | 31 | 18 |
| 도시락 | 30 | 21 |
| 무엇 | 29 | 25 |
| 지금 | 28 | 20 |
하다, 있다, 주다, 것, 거 and 되다 appear in both the most-forgotten list and the lookup data. So do 알다, 보다, 지금, 같다, 중, 들다, 오다, 좋다, 어떤 and 안녕하다.
This doesn't prove that looking a word up causes recall trouble later. It shows that learners on Lingrow struggled with some of the same words in two places: recalling a flashcard and following a live conversation.
What this means for how to learn
A short dictionary gloss is a starting point, but for abstract words it isn't enough. When a word has several uses, keep the sentence where you met it, because the sentence is what shows which use you're looking at.
For 것 or 되다, practise recalling the word inside a real sentence you have just heard. Seeing 되다 in a sentence a cafe worker said to you sticks in a way that a gloss on a card doesn't.
If you're a complete beginner, learn Hangeul and its sounds first so the word on the card is the word you hear. Our guides cover apps for learning Hangeul and Korean pronunciation for English speakers.
Lingrow's save-from-conversation flashcards were built for this. You tap a word in the transcript of a roleplay conversation, look it up, and save it as a card. Spaced repetition brings it back before you forget it. You've just heard the word in a sentence someone said to you, and that is a far better memory to attach it to than a list. Lingrow is a subscription with a free trial, and our guide to the best apps to learn Korean explains how the flashcards fit with conversation practice.
How to cite this data
This analysis uses Lingrow's own learner data. Flashcard results cover every Korean review up to 9 September 2026. Conversation lookups cover the 180 days to 9 September 2026.
Suggested citation: Lingrow, "The Korean Words Learners Forget Most, Measured (2026)", lingrow.io/blog/most-forgotten-korean-words, updated 9 September 2026. You're welcome to quote any number on this page with a link back.
This page will be updated as more data arrives. The numbers describe learners on Lingrow, not all Korean learners.
Frequently asked questions
Why do I keep forgetting Korean words?
Some Korean words carry meanings that a short dictionary gloss cannot show clearly. Among learners on Lingrow, 것 had a 65% Again rate, 되다 had 63%, and 대하다 had 62%. These words often appear inside grammar patterns, so study them in sentences, and save them from conversations once you have heard them used.
Which Korean words are hardest to remember?
For learners on Lingrow, 것 was the most forgotten card, with a 65% Again rate across 1,264 reviews by 671 learners. It was followed by 되다 at 63%, 떠나다 and 대하다 at 62%, and 등 at 59%. The ranking includes only cards reviewed at least 30 times by at least 20 learners.
What does 것 mean in Korean?
것 is a bound noun meaning thing, and in speech it shortens to 거. You mostly meet it inside grammar patterns, such as -는 것, which turns a verb phrase into a noun, or -ㄹ 것이다 for future plans. That's why a one-line gloss is hard to recall: learners on Lingrow failed it in 65% of 1,264 reviews. Learn it inside a sentence.
Are Korean verbs harder to remember than nouns?
Yes, for learners on Lingrow. Verbs had a 51% Again rate across 9,217 reviews, while nouns had a 45% Again rate across 8,765 reviews. Bound nouns such as 것 and 때문 were harder than both, at 59% across 1,680 reviews. These figures describe cards reviewed by learners on Lingrow, not every Korean word or learner.
What is the best way to remember Korean vocabulary?
Use spaced repetition, and keep the sentence with the word when the word is abstract. On Lingrow, learners tap a word in a conversation transcript, look it up and save it as a flashcard. They meet the word in a sentence first, then review it. The cards learners forgot most were mostly abstract words whose short gloss covers several uses, so those need a sentence most.
