増やす

The Japanese verb 増やす (fuyasu) is a fundamental transitive verb that translates to 'to increase,' 'to add to,' or 'to multiply.' At its core, it describes an action taken by an agent to make the quantity, volume, or amount of something larger than it was before. Unlike its intransitive counterpart 増える (fueru), which describes something increasing on its own, 増やす implies intention and direct action. This distinction is crucial for English speakers because while we often use 'increase' for both situations (e.g., 'The population increased' vs. 'We increased the population'), Japanese strictly separates the two based on who or what is causing the change. In daily life, you will encounter this word in contexts ranging from personal finance—where you want to increase your savings—to social interactions, where you might want to increase your circle of friends. It is a versatile word used in both casual conversation and formal business settings. For instance, a manager might discuss increasing production, while a student might talk about increasing their study hours. The kanji used, 増, represents an increase or an addition, and it is composed of elements suggesting earth and a repetitive action, evoking the image of piling up soil to create a larger mound. This visual helps learners remember that 増やす is about the act of 'piling on' or 'adding more' to an existing pile.

Grammar Category

Transitive Verb (他動詞 - Tadoushi)

Common Object

Quantity, amount, number, or volume (marked with を)

When using 増やす, the focus is always on the 'how' or the 'why' of the increase. It suggests a strategy or a specific effort. If you are playing a video game and you gain more lives, you might say you are 'increasing' your lives. If you are a chef and you add more salt to a soup to increase the flavor profile (though usually 'tasu' is used for ingredients, 'fuyasu' can apply to the quantity of the soup itself), you are performing the action of 増やす. It is also frequently used in abstract contexts, such as increasing one's knowledge (chishiki o fuyasu) or increasing opportunities (kikai o fuyasu). Understanding this word requires recognizing that it is an 'active' verb. You are the driver of the change. This makes it a powerful word for expressing goals, ambitions, and professional requirements. In a business report, you wouldn't just say sales went up (intransitive); you would explain how the marketing team worked to increase sales (transitive). This nuance allows for a more precise description of causality in Japanese communication.

Context: Finance

Used when talking about growing investments, savings, or capital.

Furthermore, 増やす can be used in the causative or passive forms to describe more complex social or physical interactions. For example, 'being made to increase' or 'letting someone increase.' In the context of the digital age, it is the standard word for increasing followers on social media or increasing the number of subscribers to a channel. It carries a sense of accumulation. Unlike 'tasu' (to add), which often implies adding one thing to another (like 1+1), 増やす implies a general growth in the total amount. If you have a collection of stamps and you buy ten more, you are 増やす-ing your collection. The word is deeply embedded in the Japanese psyche of improvement and growth, often appearing in self-help books and business seminars. It is a word of progress.

Register

Neutral to Formal. Suitable for all standard conversations.

Using 増やす (fuyasu) correctly requires a solid grasp of the transitive sentence structure in Japanese. The most basic pattern is [Subject] は [Object] を 増やす. However, in many Japanese sentences, the subject is omitted if it is clear from the context (usually 'I' or 'we'). The object is almost always marked with the particle を (o). This indicates that the object is receiving the action of being increased. For example, if you want to say 'I will increase the number of books,' you say Hon no kazu o fuyasu. If you want to use the polite form, it becomes fuyashimasu. In the negative, it is fuyasanai (casual) or fuyashimasen (polite). The past tense is fuyashita or fuyashimashita. These conjugations follow the standard pattern for Type 1 (Godan) verbs ending in '-su'.

Basic Pattern

[Noun] を 増やす (To increase [Noun])

One of the most common ways to use 増やす is in the ~te form to connect it with other actions or to make requests. For example, fuyashite kudasai means 'please increase (it).' This is useful in a restaurant if you want more toppings, or in a business meeting if you want more data points. Another important construction is the ~tai form for expressing desire: fuyashitai (I want to increase). This is often used when discussing personal goals. 'I want to increase my muscle mass' would be Kinniku o fuyashitai. Because 増やす is a verb of change, it often appears with ~youni suru (to make an effort to) or ~koto ni shita (decided to). For example, Yasai o fuyasu youni shite imasu (I am making an effort to increase [the amount of] vegetables [I eat]).

Potential Form

増やせる (fuyaseru) - Can increase

In more advanced usage, 増やす is used in the passive form fuyasareru to indicate that someone was forced to increase something, often with a nuance of annoyance. For example, 'I was forced to increase my workload' (Shigoto o fuyasareta). Conversely, the causative form fuyasaseru means 'to make/let someone increase.' This is common in management contexts. It's also worth noting that 増やす is frequently paired with nouns like kazu (number), ryou (amount), kikai (opportunity), and shurui (variety). When you increase the variety of products, you use shurui o fuyasu. This versatility across different types of 'increase' makes it a high-frequency verb in the Japanese language. Whether you are talking about adding more water to a vase or adding more features to a software application, 増やす is your go-to verb.

Common Mistake

Using 'ga' instead of 'o'. Remember: [Object] o fuyasu.

You will hear 増やす (fuyasu) in almost every corner of Japanese society. In the home, a parent might tell a child to increase the amount of vegetables they eat (yasai o fuyashinasai). In schools, teachers often talk about increasing the time spent on self-study or increasing the number of books read during the summer break. It is a word of encouragement and goal-setting. On television, especially during news segments about the economy, you will hear experts discussing how to increase the birth rate (shusshouritsu o fuyasu) or how companies are trying to increase their market share. In these formal contexts, while the noun-verb compound zouka saseru is also common, 増やす is used to make the speech sound more direct and accessible to the general public.

Setting: Gym/Health

'Kinniku o fuyasu' (Increase muscle) or 'Taijuu o fuyasu' (Increase weight/bulk up).

In the world of retail and customer service, 増やす is used when discussing stock and variety. A shop clerk might say they are increasing the number of colors available for a popular shirt. In advertisements, you'll see phrases like 'Increase your points!' (Pointo o fuyasou!) on loyalty card posters. This is a very common marketing tactic in Japan. Social media is another major arena for this word. Influencers often talk about strategies to increase their 'followers' (furoowaa o fuyasu) or 'likes' (ii ne o fuyasu). In this context, it carries a nuance of growth and success. If you are watching a Japanese YouTuber, they might ask their audience to help them increase their subscriber count to reach a certain milestone.

Setting: Office

'Uriage o fuyasu' (Increase sales) or 'Kouritsu o fuyasu' (Increase efficiency - though 'ageru' is more common for efficiency).

In more traditional settings, such as a tea ceremony or a craft workshop, an instructor might tell you to increase the speed of a movement or the amount of material used. In everyday conversations about hobbies, people use 増やす to talk about their collections. 'I increased my collection of vinyl records' or 'I want to increase the number of countries I've visited.' It is a word that connects to the human desire for more—more experience, more things, more connections. Because it is a 'do' verb, it always feels proactive. When you hear 増やす, you are hearing about someone's agency and their impact on the world around them. It's a word of action and results.

Setting: Kitchen

'Mizu o fuyasu' (Increase the water) when the rice is too dry.

The most frequent mistake learners make with 増やす (fuyasu) is confusing it with its intransitive partner, 増える (fueru). This is a classic 'transitivity pair' trap. In English, the word 'increase' functions as both. You can say 'The population increased' (intransitive) and 'The government increased the population' (transitive). In Japanese, you must choose. If you say Jinkou ga fuyasu, it sounds like the population itself is performing an action to increase something else, which is nonsensical. The correct forms are Jinkou ga fueru (The population increases) and Seifu ga jinkou o fuyasu (The government increases the population). Always remember: を (o) + 増やす and が (ga) + 増える.

Mistake 1

Using 'ga' with 'fuyasu'. Incorrect: Taijuu ga fuyasu. Correct: Taijuu o fuyasu.

Another common error is using 増やす when 足す (tasu - to add) or 加える (kuwaeru - to add/append) would be more appropriate. While they are similar, 増やす focuses on the result of having more in total, whereas tasu is the mathematical act of addition (1+1) and kuwaeru often implies adding a new element to a group. For example, if you are adding salt to a dish, you usually use tasu or ireru (put in). If you use 増やす, it sounds like you are increasing the overall volume of salt in the pantry or a large batch. Similarly, if you add a new member to a team, kuwaeru is more common, but if you increase the total headcount of the department from 10 to 15, 増やす is perfect.

Mistake 2

Confusing 'fuyasu' with 'ageru' (to raise). Use 'ageru' for quality, levels, or prices. Use 'fuyasu' for quantity.

Learners also sometimes struggle with the conjugation of 増やす. Because it ends in '-su', it is a Godan verb. Some learners mistakenly treat it like an Ichidan verb (like taberu) and say fuyaru or fuyate, which are incorrect. The stem is fuyashi-, so it's fuyashimasu, fuyashite, and fuyasou. Finally, be careful with the context of 'increasing speed.' While you can say supiido o fuyasu, it is much more common to say supiido o ageru (raise the speed) or hayameru (quicken). 増やす is best reserved for things that can be counted or measured in volume/amount.

Mistake 3

Using 'fuyasu' for 'enlarging' physical size. Use 'ookiku suru' for size.

Japanese has several words that overlap with 増やす (fuyasu), and choosing the right one depends on the specific nuance of 'adding' or 'increasing' you want to convey. The most direct comparison is with 足す (tasu) and 加える (kuwaeru). As mentioned, tasu is mathematical and simple addition. Kuwaeru is more formal and often implies adding something to a pre-existing mix or group to enhance it or expand it. For example, adding an ingredient to a recipe or adding a new rule to a list. 増やす, by contrast, is the most general term for increasing the total quantity or number of something.

増やす vs. 足す

'Fuyasu' is about growth in total volume/number. 'Tasu' is about the specific act of adding one thing to another (1+1).

増やす vs. 加える

'Fuyasu' is quantitative. 'Kuwaeru' often implies inclusion or appending a new element to a set.

Another set of alternatives includes 上げる (ageru) and 高める (taka-meru). These are used for 'increasing' things that aren't strictly countable in terms of units, but rather in terms of levels, quality, or intensity. You 'raise' (ageru) your salary, your speed, or your grades. You 'heighten' or 'enhance' (takameru) your skills, your awareness, or the quality of a product. If you use 増やす for these, it sounds like you are trying to count them as individual items, which often doesn't make sense. For example, 'increasing skills' (ginnou o fuyasu) would imply you are learning more types of skills, whereas 'enhancing skills' (ginnou o takameru) means you are getting better at the ones you have.

増やす vs. 拡大する

'Fuyasu' is used for numbers/amounts. 'Kakudai suru' is for the scale or physical area of something.

Finally, in formal or academic writing, you will often see 増加させる (zouka saseru). This is the causative form of the noun 'increase' (zouka). It means 'to cause an increase.' It is used in scientific papers, economic reports, and formal presentations. While 増やす is perfectly fine in these settings, zouka saseru sounds more objective and professional. For example, 'The new policy caused an increase in exports' would likely use yushutsu o zouka saseta. As a learner, mastering 増やす first is essential, as it is the most natural and common way to express the idea in 90% of situations.