〜ことができる

The grammatical structure 〜ことができる (koto ga dekiru) is a cornerstone of Japanese expression, primarily used to convey ability, capability, or the objective possibility of an action. At its heart, this phrase is a combination of three distinct parts: a verb in its dictionary form, the nominalizer koto (thing/fact), the subject marker ga, and the verb dekiru (to be able to/to come into existence). When you use this structure, you are literally saying that the 'act of doing something' is a thing that is possible or exists within your repertoire of skills.

Grammatical Function

It functions as a complex predicate where the entire preceding clause is turned into a noun phrase, allowing it to be the subject of the verb 'dekiru'.

Core Meaning

It translates most directly to 'can' or 'to be able to' in English, but it carries a slightly more formal and objective tone than the potential form of verbs.

People use this expression in a variety of contexts, ranging from simple declarations of skill to formal explanations of rules and regulations. For instance, in a job interview, you might use it to list your professional qualifications because it sounds more structured and definitive than the shorter potential form. It is also the standard way to describe the functions of a machine or the capabilities of a software program. If you are reading a manual for a new camera, you will frequently see sentences describing what the user can do with specific settings using this exact pattern.

Furthermore, this structure is essential when the verb in question does not have a commonly used potential form or when you want to emphasize the 'possibility' of an event occurring rather than a person's inherent 'ability'. For example, saying 'You can see the mountain from here' often uses this form to indicate that the environment allows for the action, rather than the person having special eyesight. It bridges the gap between 'I have the skill' and 'The situation permits'.

In social dynamics, choosing this form can also signal a level of humility or objectivity. By nominalizing the action, you create a small distance between the 'self' and the 'ability', making the statement feel less like a boast and more like a statement of fact. This is particularly useful in Japanese culture, where directness can sometimes be perceived as aggressive. By saying 'The act of speaking is possible,' you are focusing on the fact of the ability rather than your own ego.

Social Nuance

Using this form in self-introductions (jikoshoukai) provides a clear, professional summary of one's capabilities.

Finally, it is important to note that 'koto ga dekiru' is often used in negative and interrogative forms. 'Koto ga dekimasen' (cannot do) is a clear way to state a lack of ability or a prohibition, while 'Koto ga dekimasu ka?' is the standard polite way to ask if someone has a specific skill or if an action is permitted in a certain location. This versatility makes it one of the most functional patterns for intermediate learners to master.

Constructing a sentence with 〜ことができる requires a specific sequence that must be strictly followed to remain grammatically correct. The primary rule is that the verb preceding koto must always be in its **dictionary form** (also known as the plain form or the casual non-past form). You cannot use the polite -masu form or the past -ta form directly before koto in this specific 'ability' construction.

The Formula

[Verb Dictionary Form] + こと + が + できる / できます

Let's break down the components. The dictionary form of the verb provides the action (e.g., taberu - to eat). Adding koto turns that action into a noun phrase ('the act of eating'). The particle ga marks this noun phrase as the subject. Finally, dekiru (or its polite version dekimasu) expresses the possibility. This modularity is what makes Japanese grammar so logical once you understand the pieces.

When you want to express that you could do something in the past, you change the final verb dekiru into its past form dekita or dekimashita. Crucially, the verb before koto remains in the dictionary form. For example, 'I was able to go' becomes iku koto ga dekita. This is a common point of confusion for learners who might try to put the first verb into the past tense, which would change the meaning entirely or result in ungrammatical Japanese.

The structure also accommodates negative sentences easily. To say you cannot do something, change dekiru to dekinai (casual) or dekimasen (polite). This is frequently used for situational inability. For instance, if a restaurant is full, they might say hairu koto ga dekimasen (you cannot enter/we cannot seat you). This sounds more objective and less personal than saying 'I won't let you in'.

Negative Construction

[Verb Dictionary Form] + こと + が + できない / できません

Note the use of wa instead of ga in the example above. In negative sentences, ga is often replaced by wa to provide contrast or emphasis, which is a common feature across Japanese grammar. This subtle shift highlights the 'cannot' aspect of the statement. Whether you use ga or wa, the core meaning of 'possibility' remains attached to the nominalized verb phrase.

In the real world, 〜ことができる is ubiquitous, but its frequency varies depending on the setting. You are most likely to encounter it in **formal or semi-formal environments**. If you are listening to public announcements at a train station, watching a news broadcast, or reading a business contract, this form will appear constantly. It provides a level of clarity and 'officialness' that the shorter potential form lacks.

Public Announcements

'The next train can be boarded at platform 3.' Announcements use this to state objective facts about what is possible for passengers.

In the workplace, koto ga dekiru is the gold standard for describing company capabilities or personal skills. When a salesperson explains a product's features to a client, they will say, 'With this software, you can manage your inventory easily,' using kanri suru koto ga dekimasu. It sounds professional and reliable. Similarly, in academic writing or technical reports, researchers use this form to describe the results of experiments or the possibilities offered by new data.

However, in very casual daily life among friends, you might hear it less often than the potential form. If a friend asks if you can come to a party, they will likely use the potential form koreru? rather than kuru koto ga dekiru?. The latter would sound slightly stiff or like a robotic translation. That said, even in casual speech, koto ga dekiru is used when the speaker wants to emphasize the 'fact' of the possibility or when the verb is long and complex.

Another common place to find this is in **educational materials and tests** like the JLPT. Because it is a foundational grammar point, it is frequently tested to ensure learners understand how to nominalize verbs. In textbooks, it is often the first way 'can' is introduced because it doesn't require learning the complex conjugation rules of the potential form (which vary between Group 1, 2, and 3 verbs). By simply knowing the dictionary form, a student can express ability.

Instructional Manuals

'Pressing this button allows you to reset the device.' Manuals use 'koto ga dekiru' to describe functional possibilities.

Finally, you will hear this in **legal or rule-based contexts**. Signs in parks saying 'You can play with balls here' or 'You cannot enter' often use this structure. It establishes a clear boundary of what is permitted by the governing authority. In these cases, it isn't about your personal skill, but about the permission granted by the environment or the law.

One of the most frequent errors for English speakers learning 〜ことができる is using the wrong verb form before koto. Many students instinctively want to use the polite -masu form (e.g., ikimasu koto ga dekiru), but this is grammatically incorrect. The nominalizer koto requires the **plain dictionary form** to function as a noun phrase. Always double-check that you haven't accidentally 'polite-ified' the first verb.

Mistake 1: Wrong Verb Form

Incorrect: 食べますことができます (Tabemasu koto ga dekimasu).
Correct: 食べることができます (Taberu koto ga dekimasu).

Another common pitfall is confusing koto ga dekiru with the **potential form** of the verb (e.g., taberareru). While they both mean 'can', they are not always interchangeable. Using koto ga dekiru for very simple, everyday actions like 'I can eat' can sometimes sound overly dramatic or stiff in a casual conversation. Conversely, using the potential form in a formal legal document might sound too informal. The mistake here is one of **register** rather than strict grammar.

A third mistake involves the particle ga. While ga is the standard particle, beginners often forget that it changes to wa in negative sentences or for emphasis. Saying koto ga dekimasen is not 'wrong', but koto wa dekimasen is much more natural when you are denying a possibility or stating a rule. Additionally, some learners try to use o (the object marker) before dekiru because they think of 'ability' as an object, but dekiru is an intransitive verb in this context and must take ga or wa.

Finally, there is the 'Double Potential' error. This happens when a learner uses the potential form of a verb and then adds koto ga dekiru. For example, hanaseru koto ga dekimasu (I can can speak). This is redundant and sounds very strange to Japanese ears. You must choose one or the other: either the potential form of the verb (hanaseru) or the dictionary form plus koto ga dekiru (hanasu koto ga dekiru).

Mistake 2: Redundancy

Avoid: 読めることができます (Yomeru koto ga dekimasu).
Use: 読むことができます (Yomu koto ga dekimasu) OR 読めます (Yomemasu).

Lastly, learners sometimes forget that dekiru can also mean 'to be completed' or 'to be made'. In the context of koto ga dekiru, it always means 'can'. However, if you see dekiru on its own without koto, the meaning might shift. For example, yuushoku ga dekita means 'dinner is ready/done', not 'dinner can'. Context is key to ensuring you are using the 'ability' meaning correctly.

Understanding the alternatives to 〜ことができる is crucial for achieving fluency and natural-sounding Japanese. The most direct alternative is the **Potential Form** (可能形 - kanoukei). This is a conjugation of the verb itself. For Group 1 verbs, the final -u sound changes to -eru (e.g., yomu becomes yomeru). For Group 2 verbs, -ru is replaced by -rareru (e.g., taberu becomes taberareru).

Comparison: Potential Form

The potential form is much more common in daily conversation. It is shorter and feels more personal. 'Koto ga dekiru' is more objective and formal.

Another similar structure is 〜得る (uru/eru). This is a more literary or formal way to express possibility, often used in written reports or news. It suggests that something is 'possible' in a theoretical or logical sense. For example, ari-uru means 'it is possible/it could happen'. Unlike koto ga dekiru, which focuses on ability or situational permission, uru focuses on the inherent possibility of an event.

Then there is 〜わけにはいかない (wake ni wa ikanai). This is used when you cannot do something, not because you lack the skill, but because of social, moral, or situational obligations. While koto ga dekinai might mean 'I physically cannot go,' iku wake ni wa ikanai means 'I cannot go (because it would be inappropriate or I have other duties)'. This distinction is vital for intermediate learners who want to express the reason behind their inability.

For expressing 'can' in the sense of 'knowing how to', you might also see 〜方を知っている (kata o shitte iru). This literally means 'to know the way of doing'. While oyogu koto ga dekiru means 'I can swim', oyogikata o shitte iru emphasizes that you have the knowledge of how to swim. This is a subtle difference, but it's useful when you want to focus on the 'how-to' aspect of a skill.

Comparison: Potential vs. Koto ga dekiru

Potential form (~eru/rareru) is often used for spontaneous ability (e.g., 'I can see the moon'). 'Koto ga dekiru' is better for acquired skills or formal permissions.

Finally, consider 〜が可能だ (ga kanou da). This is a very formal, noun-based way to say 'is possible'. You will see this on signs, in technical specs, or in academic papers. For example, shiharai ga kanou desu (payment is possible). It is even more formal than koto ga dekiru and is rarely used in spoken conversation unless giving a very formal presentation. Mastering these variations allows you to tailor your Japanese to the specific social context you are in.