目錄
When the Korean words 「원인」「이유」「근거」 are translated into Chinese, they can easily all end up being grouped under the broad idea of “cause.” In actual sentences, however, they cannot be used quite so freely. Accidents, malfunctions, and illnesses are usually investigated in terms of their 「원인」, while taking leave, resigning from a job, or choosing something often involves explaining an 「이유」. Data, testimony, or regulations, meanwhile, may serve as the 「근거」 for a judgment. The complication is that these three words are not completely separate from one another either, so simply memorizing 「원인 = cause, 이유 = reason, 근거 = basis」 can still leave you hesitating when you encounter them in real sentences.
The difference between Korean 「원인」「이유」「근거」 can first be understood by looking at what the sentence is trying to do. Is it looking for how something happened, or explaining why someone did something? If a judgment has already been made and the question is what supports that judgment, then the sentence moves into the territory of 「근거」. Rather than drawing three rigid boundaries that can never be crossed, it is usually more practical to look at the situations and verbs each word commonly appears with.
What Is the Difference Between Korean 「원인」「이유」「근거」? Start by Looking at What Each Word Is Asking
The dictionary definitions of 「원인」「이유」「근거」 already overlap to some extent, so their differences cannot be treated as three completely separate lines. Both 「원인」 and 「이유」 can be used when discussing why a certain result occurred, and explanations of 「이유」 can also include the idea of 「근거」. A more useful way to distinguish them is to first ask whether the sentence is tracing the cause of an event, explaining the reason for an action, or asking for evidence or grounds to support a claim.
Usage ① of 「원인」｜Finding the Cause That Made Something Happen
「원인」 most commonly appears around results that have already occurred, such as accidents, illnesses, malfunctions, problems, or misunderstandings. The focus is on “what factor caused this to happen.” It therefore often appears with verbs such as 찾다, 밝히다, 규명하다, and 분석하다, meaning “find,” “identify,” “determine,” or “analyze.” For example, 「사고의 원인」 refers to investigating the cause of an accident. If it is changed to 「사고의 이유」, the nuance shifts toward “the reason the accident happened,” which is not the most natural wording in the context of an accident investigation.
- Example: 사장은 직접 이번 열차 고장의 정확한 원인을 찾아 나섰다.
Romanization: sa-jang-eun jik-jeop i-beon yeol-cha go-jang-ui jeong-hwak-han won-in-eul cha-ja na-seot-da.
Translation: The boss personally set out to find the exact cause of this train malfunction.
Here, the sentence is investigating how the malfunction happened, so 「원인」 is more natural than 「이유」. - Example: 아이들의 식중독 원인은 급식에 나온 상한 생선 때문인 것으로 밝혀졌다.
Romanization: a-i-deul-ui sik-jung-dok won-in-eun geup-sik-e na-on sang-han saeng-seon ttae-mun-in geot-eu-ro bal-kyeo-jyeot-da.
Translation: The cause of the children’s food poisoning was found to be spoiled fish served in the school meal.
Food poisoning has an identifiable causal factor that needs to be found, which is a very typical use of 「원인」. - Example: 아무래도 바이러스가 원인인 것 같습니다.
Romanization: a-mu-rae-do ba-i-reo-seu-ga won-in-in geot gat-seum-ni-da.
Translation: It seems that a virus may be the cause.
The speaker is speculating about the factor that caused the problem, so 「원인」 is used.
Usage ① of 「이유」｜Explaining Why Someone Does or Thinks Something, or Why a Certain Result Occurs
「이유」 covers a range that is more closely related to “why” than 「원인」 does. Choosing a company, resigning from a job, declining an invitation, liking something, or even explaining why a certain result occurred can all easily involve 「이유」. It is not as simple as saying that 「이유」 means a “subjective reason,” because it can also be used for objective results. However, when a sentence is asking about a person’s motivation, explanation, considerations, or a reason that can be stated, 「이유」 will usually sound more natural than 「원인」.
- Example: 민준이는 건강상의 이유로 회사에 휴직을 신청했다.
Romanization: min-jun-i-neun geon-gang-sang-ui i-yu-ro hoe-sa-e hyu-jik-eul sin-cheong-haet-da.
Translation: Minjun applied for a leave of absence from the company for health reasons.
The sentence is explaining the reason for applying for leave, not investigating the cause of an accident. - Example: 승규는 몇 가지 이유를 들어서 이번 계획은 수정되어야 한다고 주장했다.
Romanization: seung-gyu-neun myeot ga-ji i-yu-reul deu-reo-seo i-beon gye-hoeg-eun su-jeong-doe-eo-ya han-da-go ju-jang-haet-da.
Translation: Seunggyu gave several reasons and argued that this plan should be revised.
「이유를 들다」 is a common expression meaning to give or cite reasons. - Example: 이 음식을 좋아하지 않는 특별한 이유가 있나요?
Romanization: i eum-sik-eul jo-a-ha-ji an-neun teuk-byeol-han i-yu-ga in-na-yo?
Translation: Is there any particular reason you do not like this food?
The question asks about a personal reason or consideration, so 「이유」 is the most direct choice.
Usage ① of 「근거」｜Providing the Basis That Supports a Judgment or Claim
What does the Korean word 「근거」 mean? The shortest way to understand it is “the basis that supports a judgment.” 「근거」 is concerned with what allows a statement to stand. Data, testimony, legal provisions, and observations can all serve as 「근거」, so the word often appears with things such as 주장, 판단, 기소, 소문, and 논설문, where supporting material is required. A set of data may be the 「근거」 for a judgment, but that data is not necessarily the actual 「원인」 that caused the event. This distinction is important.
- Example: 검찰은 목격자의 증언을 근거 삼아 범인을 기소하였다.
Romanization: geom-chal-eun mok-gyeok-ja-ui jeung-eon-eul geun-geo sa-ma beom-in-eul gi-so-ha-yeot-da.
Translation: The prosecution indicted the suspect on the basis of the eyewitness’s testimony.
Here, the testimony is the material supporting the decision to prosecute, so 「근거」 is used. - Example: 근거도 없이 도둑으로 몰리자 매우 억울했다.
Romanization: geun-geo-do eop-si do-duk-eu-ro mol-li-ja mae-u eo-gul-haet-da.
Translation: I felt extremely wronged when I was accused of being a thief without any basis.
「근거 없이」 means that there is no sufficient basis to support the accusation. - Example: 좋은 논설문을 쓰기 위해서는 타당한 근거를 대는 연습이 필요하다.
Romanization: jo-eun non-seol-mun-eul sseu-gi wi-hae-seo-neun ta-dang-han geun-geo-reul dae-neun yeon-seup-i pil-yo-ha-da.
Translation: To write a good argumentative essay, you need practice providing valid supporting grounds.
「근거를 대다」 is a common expression for supplying reasons or material that support a claim.
Comparing 「원인」「이유」「근거」: How Do You Distinguish Cause, Reason, and Basis?
「원인」「이유」「근거」 can all appear around the question of “why did this happen?”, but they deal with somewhat different things in actual usage. 「원인」 often looks backward from a result that has already occurred and searches for the factor that caused an accident, malfunction, illness, or other problem. 「이유」 has a broader range: it can explain why a result occurred, and it is also commonly used to ask about a person’s choices, actions, or thoughts. 「근거」 usually appears after a judgment has already been made and asks what data, facts, or testimony support that statement. The three words are not completely non-overlapping, and especially in some cases both 「원인」 and 「이유」 can work. The difference often lies in whether the speaker wants to know “how this happened” or “why this is the case.”
| Comparison Item for 「원인」「이유」「근거」 | |||
| Common Chinese meaning | Cause, causal factor | Reason, cause | Basis, grounds |
| What the sentence is usually asking | What caused this result? | Why was this done or thought, or why did this result occur? | What supports this judgment or claim? |
| Common things it refers to | Accidents, illnesses, malfunctions, problems, phenomena | Actions, choices, feelings, decisions, results | Judgments, claims, inferences, accusations, legal or research conclusions |
| Main focus | The factor that produced the result | A reason that explains “why” | Material or grounds supporting a statement |
| Common collocations | 원인을 찾다／밝히다／규명하다／분석하다 | 이유를 묻다／설명하다／들다／말하다 | 근거가 있다／없다／근거를 대다／근거로 삼다 |
| Common situation | 이미 생긴 결과를 분석할 때 | 행동이나 결과에 대한 설명을 들을 때 | 판단이나 주장을 뒷받침할 내용을 요구할 때 |
▌「원인」 vs 「이유」｜The Cause That Produced a Result vs the Reason Why It Happened
「원인」 and 「이유」 are the easiest pair to confuse because both can indeed relate to “why a certain result happened.” The distinction becomes clearer in the fact that 「원인」 often treats something as a phenomenon to be analyzed and looks backward for the factor that produced the result. This is why 「원인」 is common in situations involving accidents, illnesses, malfunctions, pollution, failure, and similar problems. 「이유」 does not have the same strong analytical feel. Besides results, it is also frequently used when asking directly why a person did something, why they like or dislike something, or why they made a certain choice.
As a result, both words can appear with the topic of 「퇴사」, but they focus on different things. 「퇴사한 이유」 usually asks why a particular employee resigned—for example, because of salary, job duties, or personal plans. 「퇴사율이 높은 원인」, by contrast, sounds more like a company analyzing why its overall turnover rate is high and treating turnover as a phenomenon whose causes need to be identified.
- Example: 경찰은 사고의 정확한 원인을 조사하고 있다.
Romanization: gyeong-chal-eun sa-go-ui jeong-hwak-han won-in-eul jo-sa-ha-go it-da.
Translation: The police are investigating the exact cause of the accident.
The accident has already occurred, and the question is what factor caused it, so 「원인」 is used. - Example: 회사를 그만둔 이유를 물어봐도 될까요?
Romanization: hoe-sa-reul geu-man-dun i-yu-reul mu-reo-bwa-do doel-kka-yo?
Translation: May I ask why you left the company?
This sentence asks why the person made the choice to resign. The focus is on the person’s explanation and considerations, so 「이유」 is used. - Example: 직원들이 퇴사한 이유를 조사한 뒤, 높은 퇴사율의 원인을 분석했다.
Romanization: ji-gwon-deul-i toe-sa-han i-yu-reul jo-sa-han dwi, no-peun toe-sa-yul-ui won-in-eul bun-seok-haet-da.
Translation: After investigating the reasons employees resigned, they analyzed the causes of the high turnover rate.
The first half gathers information about “why each employee resigned,” so it uses 「이유」. The second half treats the high turnover rate as a phenomenon the company is analyzing, so it switches to 「원인」. Both words can therefore be valid within the same topic of “resignation.”
▌「이유」 vs 「근거」｜The Reason for Doing Something vs the Basis for a Judgment
「이유」 and 「근거」 can also come close in meaning, especially when someone is explaining a decision and data, costs, schedules, and other factors appear together. 「이유」 asks why a decision was made, and the answer may involve personal considerations, practical conditions, or the circumstances at the time. 「근거」 focuses more on what the judgment is based on, so it usually requires something that can support the statement, such as data, survey results, testimony, or rules.
For example, if a company decides to reduce its advertising budget, “the cost is too high” can be an 「이유」 for making that decision. But if someone says “this advertisement is ineffective” and is then asked where that conclusion comes from, “last month’s conversion-rate data” would be the 「근거」. A reason does not necessarily have to prove that a judgment is true, whereas 「근거」 itself serves to support a judgment.
- Example: 예산 부족을 이유로 다음 달 행사를 취소했습니다.
Romanization: ye-san bu-jok-eul i-yu-ro da-eum dal haeng-sa-reul chwi-so-haet-seum-ni-da.
Translation: We canceled next month’s event due to a lack of budget.
“Lack of budget” is the reason for canceling the event, and the sentence explains why the decision was made, so 「이유」 is used. - Example: 지난 분기 매출 데이터를 근거로 시장이 회복되고 있다고 판단했습니다.
Romanization: ji-nan bun-gi mae-chul de-i-teo-reul geun-geo-ro si-jang-i hoe-bok-doe-go it-da-go pan-dan-haet-seum-ni-da.
Translation: Based on last quarter’s sales data, we judged that the market was recovering.
The sales data is not “the reason the market is recovering.” It is the material supporting the judgment that “the market is recovering,” so 「근거」 is used. - Example: 지난달 데이터를 근거로 광고 예산을 줄이기로 했고, 비용 부담도 그 결정의 이유 중 하나였습니다.
Romanization: ji-nan-dal de-i-teo-reul geun-geo-ro gwang-go ye-san-eul ju-ri-gi-ro haet-go, bi-yong bu-dam-do geu gyeol-jeong-ui i-yu jung ha-na-yeot-seum-ni-da.
Translation: Based on last month’s data, we decided to reduce the advertising budget, and the cost burden was also one of the reasons for that decision.
In the same sentence, 「지난달 데이터」 supports the judgment and therefore functions as 「근거」, while 「비용 부담」 explains why the budget-reduction decision was made and therefore functions as 「이유」.
▌In the Same “User Churn” Scenario, 「원인」「이유」「근거」 Ask Different Questions
In Chinese, a phrase like “the cause of user churn” can cover many different kinds of information, but in Korean, different words can be used depending on what you want to ask. Suppose an app has recently seen a noticeable decline in users. With 「원인」, the focus is on analyzing what factors caused the overall phenomenon. With 「이유」, the perspective shifts more toward asking users themselves why they left. With 「근거」, the issue is no longer the churn itself. Instead, someone has already claimed that “a price increase caused user churn,” and the question is asking for evidence supporting that claim.
- Example: 사용자 감소의 원인을 분석하고 있습니다.
Romanization: sa-yong-ja gam-so-ui won-in-eul bun-seok-ha-go it-seum-ni-da.
Translation: We are analyzing the causes of the decline in users.
This sentence treats “the decline in users” as a phenomenon that has already occurred and then looks backward for the factors that caused it. 「원인」 gives the sentence more of a problem-analysis feel. - Example: 사용자들이 앱을 떠난 이유를 조사하고 있습니다.
Romanization: sa-yong-ja-deul-i ae-beul tteo-nan i-yu-reul jo-sa-ha-go it-seum-ni-da.
Translation: We are investigating the reasons users left the app.
With 「이유」, the perspective shifts to the users themselves. The goal is to learn why each person left—for example, because the price was too high, they did not use it often, or the features did not meet their needs. - Example: 가격 인상이 사용자 감소의 원인이라고 판단한 근거가 있나요?
Romanization: ga-gyeok in-sang-i sa-yong-ja gam-so-ui won-in-i-ra-go pan-dan-han geun-geo-ga in-na-yo?
Translation: Is there any basis for judging that the price increase was the cause of the decline in users?
This sentence contains all three layers at once. 「사용자 감소」 is the result, 「가격 인상」 is proposed as the 「원인」, and 「근거」 asks what supports that judgment. Answering the question may require cancellation surveys, usage data, or changes before and after the price increase.
Common Collocations of 「원인」「이유」「근거」: Use the Surrounding Verbs to Identify the Meaning
When 「원인」「이유」「근거」 feel similar, you can first look at the verbs that commonly appear around them. 「원인」 often appears with 찾다, 밝히다, 규명하다, and 분석하다. Expressions such as 「원인을 찾다」 and 「원인을 밝히다」 usually involve investigating why something happened. 「이유」 commonly appears with 묻다, 설명하다, 들다, and 말하다, which are used to ask for, explain, cite, or state reasons. 「근거」 often combines with 있다, 없다, 대다, and 삼다, as in 「근거가 있다」「근거를 대다」「근거로 삼다」, where the focus is on whether a judgment or claim has sufficient supporting grounds. All three words can land somewhere around “cause” in Chinese, but once they are placed back into sentences and their collocations are examined, the differences usually become easier to see.
If a sentence contains question forms such as 왜 or 뭐 때문에, you can also compare them with Korean question forms. When asking things such as “Why did you resign?”, “Why did you choose this company?”, or “Why don’t you like it?”, which concern actions, choices, or feelings, answers often involve 「이유」. If the question is investigating what caused an accident, malfunction, illness, or other problem, 「원인」 is more common. Once the question goes a step further and asks “What supports this judgment?”, the focus is no longer the cause of the event but whether there is 「근거」.
How Are 「원인」「이유」「근거」 Used in Korean News and Workplaces?
In actual usage, the differences among these three words are often tied to the purpose of the speaker. News reports investigating accidents, fires, or system failures frequently need 「원인」. Job interviews, leave requests, resignations, and explanations of decisions are more likely to involve 「이유」. Meetings, research, legal contexts, and proposals that require a judgment to be clearly supported often use 「근거」 more frequently. These are not rigid categories, but they are useful for building an initial intuition.
▌Situation ①｜System Malfunction
A：오류 원인이 뭐예요?
o-ryu won-in-i mwo-ye-yo?
What is the cause of the error?
B：서버 설정 문제로 확인됐어요.
seo-beo seol-jeong mun-je-ro hwak-in-dwae-sseo-yo.
It was confirmed to be a server configuration problem.
📌 Grammar Point: The question is looking for the factor that caused the malfunction, so 「원인」 is used.
▌Situation ②｜Explaining a Decision
A：이 결정을 한 이유가 뭐예요?
i gyeol-jeong-eul han i-yu-ga mwo-ye-yo?
What is the reason for making this decision?
B：고객 요청이 많아서요.
go-gaek yo-cheong-i ma-na-seo-yo.
Because there were many customer requests.
📌 Grammar Point: The question asks about the considerations behind making the choice, so 「이유」 is used.
▌Situation ③｜Asking for the Basis of a Judgment
A：그렇게 판단한 근거가 있나요?
geu-reo-ke pan-dan-han geun-geo-ga in-na-yo?
Is there any basis for that judgment?
B：지난달 데이터를 확인했습니다.
ji-nan-dal de-i-teo-reul hwak-in-haet-seum-ni-da.
I checked last month’s data.
📌 Grammar Point: This sentence is not asking how an event happened. It is asking for supporting material behind a judgment, so 「근거」 is used.
Word Usage Notes:
- 「원인」 often appears in investigative and analytical contexts, but this does not mean that every objective event must use only 「원인」. 「이유」 can also explain a result. The difference still needs to be judged according to what question the sentence is trying to answer.
- 「근거」 has the function of “supporting a judgment,” so it is especially common in formal proposals, news arguments, legal contexts, and research. When simply explaining why an individual did something, there is usually no need to replace 「이유」 with 「근거」.
How Do Korean 「원인」「이유」「근거」 Compare with Japanese 「原因・理由・根拠」?
Japanese 「原因」「理由」「根拠」 and Korean 「원인」「이유」「근거」 are very similar in both meaning and where they are used. 「原因」 commonly refers to the factor that produced a result, 「理由」 explains why someone did something, made a choice, or why a certain situation occurred, and 「根拠」 refers to the data, facts, or grounds that support a judgment or claim. However, these three words are not completely non-overlapping. In particular, both 「原因／理由」 and 「원인／이유」 can appear in sentences explaining why a result occurred, so actual usage still needs to be understood together with the surrounding collocations.
◆ Similar Expression: Japanese 「原因」 Refers to the Factor That Produces a Result
Japanese 「原因」 and Korean 「원인」 are both commonly used after something has already happened, looking backward to ask “what caused this result?” They are particularly common with accidents, malfunctions, illnesses, and errors, and they also combine naturally with verbs such as 「調べる」「探る」「突き止める」 that involve identifying a cause. The focus here is not on why a person made a choice, but on how the event itself occurred.
- Example: 警察は事故の原因を調べています。
Kana: けいさつはじこのげんいんをしらべています。
Translation: The police are investigating the cause of the accident.
The accident has already happened, and the current task is to identify the factor that caused it. 「事故の原因」 is used in a very similar position to Korean 「사고의 원인」. - Example: エラーの原因は設定ミスでした。
Kana: エラーのげんいんはせっていミスでした。
Translation: The cause of the error was a configuration mistake.
The configuration mistake produced the error as a result, so 「原因」 is used. Korean can similarly use 「오류의 원인」. - Example: 睡眠不足が頭痛の原因になっているかもしれません。
Kana: すいみんぶそくがずつうのげんいんになっているかもしれません。
Translation: Lack of sleep may be causing the headache.
The sentence treats sleep deprivation as a possible factor causing the headache, and 「原因になる」 is very similar in usage to Korean 「원인이 되다」.
◆ Similar Expression: Japanese 「理由」 Explains Why Something Is the Case
Japanese 「理由」 and Korean 「이유」 both commonly answer “why.” They may be used for why someone was late, why someone resigned, why someone chose a particular company, or why a certain result occurred. Compared with 「原因」, 「理由」 is more likely to appear with something that the person involved can explain or account for, but it should not therefore be memorized as referring only to a “subjective reason.”
- Example: 遅刻した理由を説明してください。
Kana: ちこくしたりゆうをせつめいしてください。
Translation: Please explain the reason you were late.
This sentence asks the person involved to explain why they were late, so 「理由」 is used. Korean can also naturally say 「지각한 이유를 설명해 주세요」. - Example: この会社を選んだ理由は何ですか。
Kana: このかいしゃをえらんだりゆうはなんですか。
Translation: What is the reason you chose this company?
The question asks what considerations led to the choice. Japanese uses 「理由」, while Korean can use 「이 회사를 선택한 이유」. - Example: 体調不良を理由に会議を欠席しました。
Kana: たいちょうふりょうをりゆうにかいぎをけっせきしました。
Translation: I missed the meeting due to poor health.
「〜を理由に」 indicates that the preceding content is being given as the reason for taking a particular action, and its structure is very similar to Korean 「○○을 이유로」.
◆ Similar Expression: Japanese 「根拠」 Refers to the Basis Supporting a Judgment or Claim
Japanese 「根拠」 and Korean 「근거」 correspond most directly. Both commonly appear with judgments, claims, inferences, or accusations and indicate what the statement is based on. Data, survey results, testimony, regulations, and other facts can all serve as 「根拠」, so expressions such as 「根拠がある／ない」「根拠にする」「何を根拠に」 are common.
- Example: その判断の根拠を教えてください。
Kana: そのはんだんのこんきょをおしえてください。
Translation: Please tell me the basis for that judgment.
The sentence is not asking why someone wants to do something, but what the judgment is based on, which is very close to Korean 「판단의 근거」. - Example: このデータを根拠に、売上が回復していると判断しました。
Kana: このデータをこんきょに、うりあげがかいふくしているとはんだんしました。
Translation: Based on this data, I judged that sales were recovering.
The data supports the judgment that follows, so 「根拠」 is used. Korean can likewise say 「이 데이터를 근거로」. - Example: 根拠のない噂を信じないでください。
Kana: こんきょのないうわさをしんじないでください。
Translation: Please do not believe baseless rumors.
「根拠のない」 means that there is no data or fact sufficient to support the claim, and its usage is almost the same as Korean 「근거 없는 소문」.
◆ Core Differences from 「원인」「이유」「근거」:
Japanese 「原因」「理由」「根拠」 and Korean 「원인」「이유」「근거」 are conceptually very close, so there is no need to memorize an entirely separate classification system. The differences are more likely to appear in conventional collocations. Japanese uses expressions such as 「原因を調べる」「理由を説明する」「根拠にする」, while Korean commonly uses 「원인을 밝히다」「이유를 들다」「근거로 삼다」. In addition, both 「理由／이유」 have a broader range than merely expressing a person’s subjective motivation and can also explain why certain results occur.
「원인」「이유」「근거」 tend to get mixed together because the Chinese word “原因” can cover a very broad range, while Korean often separates these situations into different expressions. If you are investigating why an accident happened, you may be looking for its 「원인」. If you are explaining why someone resigned, refused something, or made a choice, you will usually use 「이유」. If a judgment needs support from data, testimony, or other material, then the issue is 「근거」.
When you encounter these words in actual sentences, you also do not need to begin by recalling three abstract Chinese definitions. When you see 원인을 찾다 or 원인을 밝히다, think first of investigating how something happened. When you see 이유를 묻다 or 이유를 설명하다, the sentence is usually asking for or explaining a reason. When you see 근거가 있다 or 근거로 삼다, the focus is on whether a statement has supporting grounds. The meanings of Korean 「원인」「이유」「근거」 do overlap, but their common collocations and usage contexts are usually enough to distinguish the three.
FAQs
「원인」 focuses more on the causal factor that produced a result, while 「이유」 is more commonly used to explain the reason behind an action, choice, feeling, or result. The two overlap, so they should not be rigidly divided into “objective vs subjective.” Accident investigations often look for 「원인」, while questions about reasons for resigning, making choices, or having preferences commonly use 「이유」.
「근거」 refers to the basis or grounds supporting a judgment, claim, or decision. Data, testimony, legal provisions, or observations can all serve as 「근거」. It answers the question “What supports this judgment?” and is not necessarily the 「원인」 that caused an event.
Their meanings can be close in some contexts, but they are not completely interchangeable. 「퇴사의 이유」 commonly refers to the reason a particular person resigned, while 「퇴사의 원인」 sounds more like an analysis of the causes behind the phenomenon of resignation. Changing the word can also change the perspective of the sentence.
First look at what question the sentence is answering. If it asks what caused a result, 「원인」 is usually the better choice. If it asks why someone did something or why something is the case, 「이유」 is common. If it asks what supports a judgment or claim, use 「근거」. Checking the surrounding verbs can make the distinction even clearer.
The Chinese word “原因” can cover several different semantic roles that Korean tends to separate, so a word-for-word correspondence is not enough. 「원인」 is closer to a causal factor, 「이유」 to a reason, and 「근거」 to supporting grounds. In ambiguous sentences, first decide whether the sentence is dealing with causation, explaining a reason, or supporting an argument.