増える vs. 増す: What Is the Difference in Japanese?

Introduction

The Japanese verbs 「増える」(fueru) and 「増す」(masu) both describe something becoming greater than before.

Because their meanings overlap, learners often wonder whether they can be used interchangeably.

For example:

• 人が増える
• 不安が増える
• 不安が増す
• 重要性が増す

All of these expressions involve an increase, but the type of increase is different.

The key is to identify whether the sentence is mainly describing an increase in number or amount, or an increase in degree, strength, or intensity.

The Main Difference

Here is the simplest way to remember the distinction:

• 「増える」(fueru) is mainly used when a number, quantity, amount, or frequency becomes larger.
• 「増す」(masu) is mainly used when a degree, strength, importance, intensity, or momentum becomes greater.

A useful shortcut is:

• More people or things → 「増える」
• Stronger feelings or intensity → 「増す」

This is not an absolute rule. 「増す」 can sometimes be used for quantities, and 「増える」 can also be used with abstract ideas. However, this basic distinction will help you choose the more natural word in most situations.

What Does 「増える」 Mean?

「増える」(fueru / to increase, to become more) describes a change in which a number, amount, quantity, or frequency becomes greater.

It is commonly used with things that can be counted or measured.

Typical combinations include:

• 人が増える
  The number of people increases.

• 仕事が増える
  The amount of work increases.

• 体重が増える
  Body weight increases.

• 収入が増える
  Income increases.

• 利用者が増える
  The number of users increases.

• 選択肢が増える
  The number of available choices increases.

「増える」 is a very common, neutral verb. It is natural in both everyday conversation and written Japanese.

When the sentence is about how many people, things, tasks, or opportunities there are, 「増える」 is usually the safest choice.

What Does 「増す」 Mean?

「増す」(masu / to increase, to intensify) is often used when a degree, intensity, strength, importance, or momentum becomes greater.

It is especially common with abstract ideas that are difficult to count directly.

Typical combinations include:

• 不安が増す
  Anxiety grows stronger.

• 期待が増す
  Expectations become greater.

• 重要性が増す
  Importance increases.

• 関心が増す
  Interest grows.

• 緊張が増す
  Tension intensifies.

• 勢いが増す
  Momentum increases.

• 深刻さが増す
  The situation becomes more serious.

Compared with 「増える」, 「増す」 sounds slightly more formal and literary. It often appears in news reports, essays, business documents, and JLPT reading passages.

「増す」 can also be used with the particle 「を」, as in:

• 勢いを増す
  To gain momentum.

• 速度を増す
  To increase speed.

This grammatical pattern is an important clue in JLPT questions.

Differences in Usage

「増える」 in Everyday Conversation

「増える」 is widely used in daily conversation.

It is natural when talking about work, money, weight, people, possessions, or other concrete quantities.

最近、仕事が増えました。
My workload has increased recently.

外国人の観光客が増えています。
The number of international tourists is increasing.

少し体重が増えてしまいました。
I have gained a little weight.

In each case, the speaker is describing an increase in a measurable amount or number.

「増す」 in Formal Writing and News

「増す」 is particularly common in formal explanations, news articles, reports, and academic writing.

国際社会で環境問題の重要性が増している。
The importance of environmental issues is growing in the international community.

今後の経済に対する不安が増している。
Anxiety about the future economy is increasing.

両国の対立は、さらに深刻さを増している。
The conflict between the two countries is becoming even more serious.

Using 「増す」 emphasizes that a condition or quality is becoming stronger or more intense.

「増す」 in Business Japanese

In business writing, 「増す」 is frequently used with words such as importance, necessity, interest, expectations, and competition.

情報管理の重要性が増しています。
The importance of information management is increasing.

海外市場への関心が増しています。
Interest in overseas markets is growing.

新しいサービスへの期待が増しています。
Expectations for the new service are rising.

Expressions such as 「重要性が増える」 and 「関心が増える」 are also grammatically possible. However, 「増す」 often sounds more polished and suitable for a formal report.

Examples with 「増える」

Example 1

日本語を勉強する外国人が年々増えています。
The number of international learners studying Japanese is increasing every year.

This sentence describes an increase in the number of people, so 「増える」 is the natural choice.

Example 2

新しい仕事が増えて、毎日忙しいです。
I have more new tasks now, so I am busy every day.

The number or amount of tasks has become greater.

Example 3

運動をやめたら、体重が三キロ増えました。
After I stopped exercising, I gained three kilograms.

Body weight is a measurable quantity, so 「増える」 is used.

Example 4

オンラインで受けられる授業の選択肢が増えました。
There are now more options for classes that can be taken online.

The number and variety of choices have increased.

Examples with 「増す」

Example 1

試験の日が近づくにつれて、不安が増してきました。
As the exam day approached, my anxiety grew stronger.

The sentence focuses on the increasing intensity of the speaker’s anxiety.

Example 2

インターネット上の情報を確認する重要性が増しています。
The importance of checking information found online is increasing.

The degree of importance is becoming greater.

Example 3

夜になると、雨と風がさらに強さを増しました。
At night, the rain and wind became even stronger.

「強さを増す」 means that the level of strength or intensity increases.

Example 4

その選手は、試合が進むにつれて勢いを増していきました。
The athlete gained momentum as the match progressed.

The athlete’s energy and momentum became stronger.

Example 5

車は速度を増しながら、坂道を下っていきました。
The car went down the hill while increasing its speed.

Here, 「増す」 is used with 「を」 in the expression 「速度を増す」.

A Subtle Difference: 心配事が増える and 心配が増す

Some expressions may look similar but focus on different kinds of change.

心配事が増える

心配事が増える。
The number of things to worry about increases.

This means that there are now more sources of worry, such as work, family, money, or health problems.

The number of problems has increased.

心配が増す

心配が増す。
The feeling of worry grows stronger.

Even if there is only one problem, the person may feel increasingly worried about it.

The difference is:

• 心配事が増える: There are more reasons or problems to worry about.
• 心配が増す: The emotional intensity of worry becomes stronger.

Common Mistakes

Use 「増える」 for People and Objects in Ordinary Conversation

The following sentence may appear in formal writing, but it sounds somewhat stiff in everyday conversation:

この町では外国人が増しています。
The number of foreign residents in this town is increasing.

In ordinary conversation, this is more natural:

この町では外国人が増えています。
The number of foreign residents in this town is increasing.

Because the sentence describes an increase in the number of people, 「増える」 is the standard choice.

Other natural examples include:

• 家族が一人増えました。
  Our family has gained one new member.

• 店の商品が増えました。
  The number of products in the store has increased.

• 会議の回数が増えました。
  The number of meetings has increased.

Do Not Use 「増える」 Directly with 「を」

「増える」 is an intransitive verb. It normally describes something increasing by itself, so it is used with 「が」 rather than 「を」.

Incorrect:

速度を増える。

Natural alternatives:

速度が増える。
The speed increases.

速度を増す。
To increase speed.

When a person or organization intentionally increases something, use 「増やす」(fuyasu / to increase something).

生産量を増やす。
To increase production.

Remember:

• 増える: Something becomes more.
• 増す: A degree or intensity increases; it can also appear with 「を」.
• 増やす: Someone intentionally makes something increase.

Abstract Nouns Can Also Be Used with 「増える」

Sentences such as the following are not grammatically wrong:

• 不安が増える
• 関心が増える
• 重要性が増える

However, 「増す」 often makes the increase in degree or intensity sound clearer and more formal.

• 不安が増える
  Anxiety increases in a general sense.

• 不安が増す
  Anxiety grows stronger or more intense.

The best choice may depend on the writing style and the surrounding context.

How to Choose on the JLPT

In JLPT vocabulary and reading questions, look carefully at the noun, the particle, and the writing style.

Choose 「増える」 for Numbers and Quantities

「増える」 is likely to be correct when the sentence contains nouns such as:

• 人数
• 件数
• 回数
• 荷物
• 仕事
• 収入
• 体重
• 利用者

For example:

高齢者の一人暮らしが年々増えている。
The number of elderly people living alone is increasing every year.

The sentence describes a growing number of people, so 「増える」 is natural.

Choose 「増す」 for Degree and Intensity

「増す」 is likely to be correct with nouns such as:

• 不安
• 期待
• 重要性
• 必要性
• 緊張
• 関心
• 勢い
• 深刻さ

For example:

個人情報を守ることの重要性が増している。
The importance of protecting personal information is increasing.

The degree of importance is becoming greater.

Check the Particle

「増える」 normally does not take a direct object marked by 「を」.

When you see expressions such as the following, 「増す」 may be the correct answer:

• 勢いを増す
• 速度を増す
• 輝きを増す
• 深刻さを増す

However, if 「増やす」 is also an option, check whether someone is intentionally increasing something.

Check the Style of the Passage

In conversational and everyday contexts, 「増える」 is more common.

In news articles, social commentary, formal explanations, and business documents, 「増す」 often appears with abstract nouns.

When you are unsure, ask yourself:

• Is the number or quantity becoming larger?
• Is the degree, intensity, or momentum becoming stronger?
• Is the particle 「が」 or 「を」 being used?
• Is the sentence conversational or formal?

These four questions can help you select the more natural answer.

Summary

Both 「増える」 and 「増す」 describe something becoming greater, but they are used differently.

• 「増える」 is mainly used when a number, amount, quantity, or frequency becomes greater.
• 「増す」 is mainly used when a degree, importance, strength, or intensity becomes greater.
• 「増える」 is common in everyday conversation.
• 「増す」 is common in formal writing, news, and JLPT reading passages.
• 「増す」 can be used in expressions such as 「勢いを増す」 and 「速度を増す」.

Learning the dictionary meanings of Japanese words is not always enough. To choose naturally between similar words, you need practice recognizing which words commonly appear together.

At RJT（Rapid Japanese Training）, you can practice Japanese vocabulary and grammar through short JLPT-style questions. By repeatedly choosing the most natural expression in context, you can build the judgment skills needed for both the JLPT and real Japanese communication.