増える vs 増やす
JLPT N4 vocabulary · what is the difference?
増える is a number going up by itself (人が増える, the number of people grows); 増やす is someone deliberately raising it (時間を増やす, you increase the time). Both want something countable or measurable — if what grows is a degree or a feeling rather than a quantity, 増す is the natural verb instead.
When to use each
増える
ふえる
Use 増える when an amount or number rises with no one named as raising it: population, your weight, the number of tourists. It takes が.
この町の人が増えました。
このまちのひとがふえました。
The number of people in this town has gone up.
最近、体重が増えてきました。
さいきん、たいじゅうがふえてきました。
Lately my weight has been going up.
増やす
ふやす
Use 増やす when someone chooses to raise an amount: study hours, staff numbers, the size of a portion. It takes を, and there is an intention behind it.
勉強の時間を増やします。
べんきょうのじかんをふやします。
I'm going to increase my study time.
店は店員を二人増やしました。
みせはてんいんをふたりふやしました。
The shop added two more staff.
Sentences where only one works
去年から外国人の観光客が増えています。
きょねんからがいこくじんのかんこうきゃくがふえています。
Foreign tourists have been increasing since last year.
Nobody raises the tourist count on purpose, so 増える. 増やしています would need someone doing it.
会社は工場を三つに増やしました。
かいしゃはこうじょうをみっつにふやしました。
The company increased its factories to three.
The company is the agent and 工場 the object, so 増やす with を; に marks the resulting number.
不安が増しています。
ふあんがましています。
The unease is growing.
For feelings and degrees rather than counts, 増す is natural; 不安が増える sounds like you are counting separate worries.
Common mistakes
体重を増えました。
体重が増えました。
増える cannot take を. If you put on weight deliberately, say 体重を増やしました.
給料が増やしました。
給料が増えました。
With が you need the intransitive. 給料を増やしました would mean you yourself raised the salary, which only the employer can do.
背が増えました。
背が伸びました。
Height is not a count going up; growing taller is 伸びる.
Frequently asked questions
Which do I use for my own weight going up?
体重が増えました — it happened to you rather than being your plan. 体重を増やす suits athletes and others bulking up on purpose.
What is the difference between 増える and 増す?
増える counts things and is the everyday word. 増す is more formal and works with degree — 不安が増す, スピードを増す — and appears mainly in writing and news.
Is 増やす only for numbers?
It works for anything measurable you can deliberately raise: time, money, portions, staff. For abstract qualities such as confidence, 高める is more natural.