基づく

The Japanese verb 基づく (motozuku) is a fundamental vocabulary word, especially for learners at the CEFR B1 level and above, as it introduces the ability to express the foundation, origin, or basis of an idea, action, or physical entity. To fully grasp its meaning, we must first look at the kanji used to write it: 基. This kanji is read as 'ki' in its onyomi (Chinese reading) and 'moto' in its kunyomi (Japanese reading). It carries the core meaning of 'foundation,' 'basis,' or 'origin.' When combined with the verb suffix 'づく' (dzuku), which is a voiced version of 'つく' (tsuku, meaning to attach or to take root), the word literally translates to 'to take root in a foundation' or 'to attach to a basis.' This etymological breakdown perfectly encapsulates its modern usage: to be based on something, to originate from a specific source, or to be founded upon a particular set of principles, data, or facts. Understanding this word is crucial for navigating academic, professional, and formal contexts in Japanese, where justifying one's statements or actions with evidence is paramount.

Core Definition

To be based on, to be founded on, to originate from. It indicates the underlying foundation of an abstract concept such as a theory, a plan, a story, or a decision.

When you use 基づく, you are explicitly stating that there is a logical, factual, or historical precedent for what is being discussed. For example, if a new company policy is introduced, it is rarely created out of thin air; rather, it is 'based on' (基づく) recent market research or employee feedback. In literature and entertainment, you will frequently encounter this word in the phrase '実話に基づく' (jitsuwa ni motozuku), which translates to 'based on a true story.' This specific phrase is a staple in movie trailers, book blurbs, and documentary introductions, serving as a powerful hook to draw audiences in by promising authenticity. The versatility of 基づく allows it to bridge the gap between abstract concepts and concrete evidence, making it an indispensable tool for persuasive communication and logical reasoning in Japanese.

Nuance of Formality

While not strictly formal, 基づく elevates the tone of a sentence. It sounds more objective and analytical than simply saying something comes from somewhere else.

Furthermore, it is important to distinguish 基づく from similar words that might translate to 'based on' in English but carry different nuances in Japanese. For instance, while 基づく focuses on the logical or factual foundation, words like 沿う (sou) mean 'to follow along' a guideline or policy, and 則る (nottoru) means 'to conform to' a rule or tradition. 基づく is unique in its emphasis on the *origin* of the rationale. If a decision is made 'based on the law' (法律に基づく), it means the law provided the foundational justification for that decision. This distinction is vital for learners who wish to express themselves with precision and clarity, avoiding the common pitfall of using a one-size-fits-all translation for complex English prepositions or phrasal verbs.

In addition to its use in everyday professional and academic language, 基づく also appears frequently in legal and bureaucratic contexts. Laws, regulations, and official guidelines are often cited as the basis for governmental actions or corporate compliance measures. In these scenarios, the word conveys a sense of authority and legitimacy. When a government official states that a measure was taken '法律に基づいて' (houritsu ni motozuite - based on the law), they are invoking the power of the legal system to validate their action. This usage highlights the word's capacity to convey not just a factual basis, but also a legal or moral imperative, further cementing its status as a key vocabulary item for advanced comprehension of Japanese society and its administrative functions.

Abstract vs Physical

Crucially, 基づく is used almost exclusively for abstract foundations (ideas, data, laws). It is NOT used for physical foundations, like a house based on a concrete slab.

To truly master 基づく, learners should actively practice incorporating it into their own speech and writing. Start by identifying the 'basis' of your opinions or arguments. Instead of simply saying 'I think X because Y,' try framing it as 'Based on Y, I think X' (Yに基づいて、Xだと思います). This subtle shift in phrasing not only demonstrates a higher level of language proficiency but also makes your arguments sound more structured, objective, and persuasive. As you continue to encounter and use this word in various contexts, its nuances and applications will become increasingly intuitive, allowing you to express complex relationships between ideas and their foundations with confidence and accuracy.

Mastering the grammatical usage of 基づく (motozuku) is essential for integrating it smoothly into your Japanese communication. As a Godan verb ending in 'ku', it follows standard conjugation patterns, but its syntactic behavior within a sentence is what requires the most attention. The absolute most critical rule to remember is that 基づく is an intransitive verb that takes the particle に (ni) to mark the foundation or basis. The core formula is always [Foundation/Basis Noun] + に + 基づく. You cannot use the object particle を (wo) with 基づく in its standard form, because the subject of the sentence is the thing that *is* based on the foundation, not the foundation itself. For example, 'The plan is based on data' translates to 計画はデータに基づく (Keikaku wa deeta ni motozuku). The data is the foundation (marked by に), and the plan is the subject (marked by は or が).

Conjugation: Te-form

The te-form is 基づいて (motozuite). This is incredibly common and translates to 'based on [X], [Action happens]'. Example: データに基づいて決定する (Decide based on data).

One of the most frequent ways you will use and encounter 基づく is when it modifies another noun. In Japanese, verbs can directly modify nouns by being placed immediately before them. When doing this with 基づく, you have two primary options: using the dictionary form (に基づく) or the past/perfective form (に基づいた). For instance, 'a story based on facts' can be translated as 事実に基づく物語 (jijitsu ni motozuku monogatari) or 事実に基づいた物語 (jijitsu ni motozuita monogatari). In most contexts, these two forms are interchangeable and carry the same meaning. However, some native speakers feel a slight nuance: に基づく sounds slightly more objective and continuous, as if the foundation is an ongoing, immutable truth, while に基づいた emphasizes that the act of establishing the foundation has already been completed. For learners, treating them as synonyms is perfectly acceptable and practical.

Noun Modification

To describe a noun, use [Basis] + に基づく + [Noun] OR [Basis] + に基づいた + [Noun]. Both are grammatically correct and highly natural.

Another vital grammatical structure involves using the te-form of the verb: 基づいて (motozuite). This form functions as a conjunction, linking the basis to a subsequent action. It translates smoothly to 'based on [X], I will do [Y].' This is the form you need when you want to describe an action that is guided by a specific foundation. For example, 'We will proceed with the project based on the client's request' becomes 顧客の要望に基づいて、プロジェクトを進めます (Kokyaku no youbou ni motozuite, purojekuto o susumemasu). Notice how the te-form connects the foundation (the request) to the active verb (proceeding). This structure is ubiquitous in business Japanese, where actions must constantly be justified by referring to policies, requests, or data.

For advanced learners, it is worth noting the transitive counterpart to 基づく, which is 基づける (motozukeru). While 基づく describes the state of being based on something (The theory is based on data), 基づける describes the active process of grounding or establishing something upon a foundation (The scientist based the theory on data). The structure for the transitive verb is [Foundation] + に + [Object] + を + 基づける. For example, 彼は自分の主張を証拠に基づけた (Kare wa jibun no shuchou o shouko ni motozuketa - He based his argument on evidence). While 基づける is less common in everyday conversation than 基づく, it is a powerful word in academic writing and formal debate, allowing the speaker to emphasize the active construction of an argument or theory.

Negative Form

The negative form is 基づかない (motozukanai), meaning 'not based on'. It is often used to criticize arguments or plans that lack a solid foundation.

Finally, let's look at how to use 基づく in negative sentences. The negative plain form is 基づかない (motozukanai), and the negative te-form is 基づかなくて (motozukanakute) or 基づかずに (motozukazuni). You will often hear the phrase 事実に基づいていない (jijitsu ni motozuite inai), which means 'it is not based on facts.' This is a polite but firm way to point out that someone's statement is baseless or incorrect. Another common negative construction is 〜に基づかないで (not based on ~), used when describing an action taken without a proper foundation. For example, 憶測に基づかないで発言してください (Okusoku ni motozukanaide hatsugen shite kudasai - Please do not speak based on speculation). Mastering these negative forms allows you to critically evaluate information and express skepticism clearly and professionally in Japanese.

The verb 基づく (motozuku) is ubiquitous across a wide spectrum of Japanese contexts, primarily those that demand a degree of formality, objectivity, or logical justification. One of the most common places you will encounter this word is in the realm of news and journalism. Reporters and news anchors frequently use 基づく to attribute information to its source, thereby establishing the credibility of their reports. For example, you might hear phrases like 警察の発表に基づく (based on the police announcement) or 政府の統計に基づく (based on government statistics). In these instances, the word serves as a crucial linguistic tool for journalistic integrity, clarifying that the information being presented is not mere speculation but is grounded in official or verifiable data. This usage is so prevalent that any learner aiming to understand Japanese news broadcasts or read newspapers must become intimately familiar with it.

News and Media

Extensively used to cite sources, official announcements, and statistical data to ensure journalistic credibility and objectivity.

Beyond the news, the business world is another major domain where 基づく reigns supreme. In corporate environments, decisions, strategies, and proposals are rarely accepted without a solid foundation. Therefore, business professionals constantly use 基づく to justify their ideas. When presenting a new marketing strategy, a manager might say, 市場調査の結果に基づいて、この戦略を提案します (I propose this strategy based on the results of the market research). Similarly, performance evaluations, budget allocations, and company policies are all formulated 'based on' specific criteria or guidelines (評価基準に基づく, 予算案に基づく). In Japanese business culture, where consensus and logical progression are highly valued, the ability to clearly articulate the basis of your proposals using 基づく is a key marker of professional competence.

Business Contexts

Crucial for proposals, reports, and strategic planning. It demonstrates that decisions are data-driven rather than arbitrary.

The academic and scientific communities also rely heavily on 基づく. In research papers, university lectures, and scientific discussions, the word is indispensable for linking theories to evidence. A scientist might explain that their new hypothesis is 'based on previous experiments' (先行実験に基づく), or a historian might argue that their interpretation of an event is 'based on newly discovered documents' (新発見の資料に基づく). In these contexts, 基づく is the linguistic glue that holds logical arguments together, demonstrating the chain of reasoning from empirical evidence to theoretical conclusion. For students studying in Japan or researchers collaborating with Japanese colleagues, mastering the academic nuances of this word is absolutely essential for effective communication and participation in scholarly discourse.

Furthermore, 基づく is deeply embedded in legal and administrative language. Laws, regulations, and contracts form the foundation of societal operations, and actions taken within these frameworks are constantly described as being 'based on' them. A city office might issue a notice stating that a certain procedure is required '法律に基づいて' (based on the law), or a contract might stipulate that disputes will be resolved '本契約の条項に基づいて' (based on the clauses of this contract). This legalistic usage highlights the binding nature of the foundation; when something is based on a law or contract, it is not merely a suggestion, but a requirement. Understanding this authoritative nuance is important when navigating official procedures or reading formal documents in Japan.

Entertainment

Frequently seen in movie trailers, book covers, and TV show intros to indicate that the fictionalized work has real-world origins.

Finally, on a lighter note, you will frequently encounter 基づく in the entertainment industry, particularly in the context of storytelling. The phrase 実話に基づく (jitsuwa ni motozuku - based on a true story) is a marketing staple for movies, novels, and television dramas. It is used to add weight and emotional resonance to a narrative by assuring the audience that the events depicted, however incredible, have roots in reality. Similarly, adaptations of books into movies are often described as 原作に基づく (gensaku ni motozuku - based on the original work). Even in casual conversations about pop culture, you might hear someone explain that a character's design is 'based on a historical figure' (歴史上の人物に基づく). This widespread usage across diverse fields underscores the versatility and importance of 基づく in the Japanese language.

While 基づく (motozuku) is a highly useful verb, its specific nuances and grammatical requirements often lead to common mistakes among Japanese learners. The most frequent error is undoubtedly particle misuse. Because the English translation is 'based ON,' learners often intuitively reach for the particle で (de), which indicates the means or location of an action, or even を (wo), the direct object marker. However, 基づく strictly requires the particle に (ni) to mark the foundation. Saying データで基づく (deeta de motozuku) or データを基づく (deeta o motozuku) is grammatically incorrect and sounds very unnatural to native speakers. The correct formulation is always データに基づく (deeta ni motozuku). Remembering that に often points to a target, destination, or in this case, the point of origin or foundation, can help solidify this rule in your mind.

Particle Error

Using で (de) or を (wo) instead of に (ni). Always use [Noun] + に + 基づく.

Another significant area of confusion arises from applying 基づく to physical foundations. In English, we can say 'The house is based on a concrete foundation' or 'The statue is based on a wooden pedestal.' It is tempting to translate this directly using 基づく, but this is a critical mistake. 基づく is reserved almost exclusively for abstract concepts—ideas, laws, data, stories, plans, and theories. If you want to talk about a physical foundation, you need to use different vocabulary, such as 土台にする (dodai ni suru - to use as a foundation) or 基礎を置く (kiso o oku - to lay a foundation). Using 基づく for physical objects (e.g., 家はコンクリートに基づく) sounds nonsensical in Japanese, as it implies the house is logically derived from the concept of concrete, rather than physically built upon it.

Physical vs Abstract

Never use 基づく for physical buildings or objects resting on a physical base. It is strictly for abstract, logical, or informational foundations.

Learners also frequently struggle with the distinction between 基づく (motozuku) and its transitive counterpart, 基づける (motozukeru). As mentioned earlier, 基づく is intransitive; the subject *is* based on something. 基づける is transitive; someone *bases* an object on something. A common mistake is trying to use 基づく when you are the one actively creating the foundation. For example, if you want to say 'I based my report on the survey,' you cannot say 私はレポートをアンケートに基づく (Watashi wa repooto o ankeeto ni motozuku). This mixes transitive and intransitive structures. You must either use the te-form as a conjunction: アンケートに基づいてレポートを書いた (I wrote the report based on the survey), or use the transitive verb: レポートをアンケートに基づけた (I based the report on the survey). The te-form approach is generally much more natural and common in everyday Japanese.

Furthermore, there is a tendency to overuse 基づく in casual conversation where simpler expressions would suffice. While 基づく is not overly stiff, it does carry a tone of objective analysis. If a friend asks why you chose a certain restaurant, replying with ネットのレビューに基づく判断です (It is a judgment based on internet reviews) sounds robotic and overly formal. In casual speech, it is much more natural to use simpler structures like ネットのレビューを見て決めた (I decided after looking at internet reviews) or レビューが良かったから (Because the reviews were good). Understanding the register—the appropriate level of formality—is just as important as understanding the grammar. Save 基づく for situations where you need to sound professional, objective, or when discussing serious topics like news, business, or academics.

Over-formality

Using 基づく in highly casual, everyday situations can make you sound unnatural or overly academic. Match the word to the formality of the context.

Finally, a minor but persistent spelling and pronunciation error involves confusing the voiced 'zu' (づ) with the other voiced 'zu' (ず). Because 基づく comes from the verb つく (tsuku), it must be written with づ (the voiced version of つ), not ず (the voiced version of す). Typing 'motozuku' on a Japanese keyboard usually yields the correct kanji, but if you are writing by hand or spelling it out in hiragana, writing もとずく is a spelling error. Always remember the etymology: 基 (moto) + つく (tsuku) = 基づく (motozuku with づ). Keeping this origin in mind will not only help you spell it correctly but also reinforce its core meaning of 'taking root' or 'attaching' to a foundation.

The Japanese language is rich in vocabulary that expresses the concept of origin, foundation, or adherence to a standard. While 基づく (motozuku) is one of the most versatile and common of these words, understanding its synonyms and related terms is crucial for expanding your expressive range and grasping subtle nuances in different contexts. One of the closest synonyms is 拠る (yoru), often written in hiragana as よる. When used in the pattern 〜による (ni yoru) or 〜によって (ni yotte), it can translate to 'due to,' 'depending on,' or 'based on.' However, 拠る has a broader scope than 基づく. While 基づく specifically implies a logical or factual foundation (like data or a true story), 拠る can indicate cause, means, or reliance. For example, 噂によると (according to rumors) uses よる, but you would not use 基づく here because rumors are not a solid, factual foundation. 基づく is stricter and implies a more solid, reliable base.

拠る (yoru)

Broader than 基づく. Can mean 'due to', 'depending on', or 'based on'. Often used for sources of information (e.g., 'according to the news').

Another highly relevant word is 準拠する (junkyo suru). This is a formal, Sino-Japanese (kango) term that means 'to conform to' or 'to be based on a standard.' While 基づく can be used for a wide variety of foundations (data, experience, stories), 準拠する is almost exclusively used when referring to strict rules, standards, guidelines, or official formats. For instance, if a software program is built to follow a specific international standard, you would say 国際規格に準拠している (It conforms to international standards). You could use 基づく here, but 準拠する emphasizes strict adherence and compliance to a predefined rule set, making it the preferred choice in technical, legal, and highly formal bureaucratic documents.

準拠する (junkyo suru)

Highly formal. Means to conform strictly to a standard, rule, or guideline. Used in technical and legal contexts.

A related concept is expressed by the verb 則る (nottoru), which means 'to conform to,' 'to follow,' or 'to act in accordance with.' Like 準拠する, it implies following a rule, but 則る is often used with more abstract, traditional, or moral standards, such as customs, precedents, or sportsmanship. For example, 伝統に則った儀式 (a ceremony in accordance with tradition) or ルールに則って戦う (to fight according to the rules). The difference between 則る and 基づく lies in the action: 基づく focuses on the *origin* of the idea or plan, while 則る focuses on the *action* of following a prescribed path or standard. You base a plan on data (基づく), but you execute the plan in accordance with the rules (則る).

We must also consider the verb 踏まえる (fumaeru). Literally meaning 'to step on,' its figurative meaning is 'to take into account,' 'to bear in mind,' or 'to base one's actions on a premise.' The nuance here is slightly different from 基づく. When you use 基づく, the foundation is the primary, direct source of the outcome. When you use 踏まえる, the foundation is a condition or a piece of context that you have considered before taking action. For example, 現状を踏まえて計画を立てる (to make a plan taking the current situation into account). The current situation isn't necessarily the *only* basis for the plan, but it is a crucial factor that has been mentally 'stepped on' or acknowledged during the planning process. 踏まえる implies a more complex decision-making process where multiple factors might be considered.

踏まえる (fumaeru)

Means to take into account or consider a premise. It implies acknowledging a situation before acting, rather than a direct logical derivation.

Finally, there is 根ざす (nezasu), which literally means 'to take root.' It is used metaphorically to mean 'to be rooted in' or 'to stem from.' While 基づく is often used for objective data, laws, or specific events, 根ざす is typically used for deep-seated, long-standing cultural, psychological, or historical phenomena. For example, you would say 地域の文化に根ざした習慣 (customs rooted in local culture) or 深い不信感に根ざしている (rooted in deep distrust). 根ざす conveys a sense of organic growth and deep, almost inseparable connection to the origin, whereas 基づく is more analytical and structural. By understanding these subtle distinctions—from the broad 拠る to the strict 準拠する, the compliant 則る, the considerate 踏まえる, and the deeply rooted 根ざす—you can choose the exact word that perfectly captures your intended meaning, elevating your Japanese from merely correct to highly expressive and natural.