You know when A just keeps getting more and more B?

Or when X just continues to Y?

There's a phrase for that:

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JLPT N3: いっぽうだ (just keeps on; will just continue to)

一方 (いっぽう) means "one way," "one direction," "one side."

When we get fancy and do grammar stuff, though, 一方 means all kinds of things.

Case in point:

貧富の差は広がる一方です。
ひんぷ　の　さ　は　ひろがる　いっぽう　です。
Wealth inequality just continues to increase.
Literally: “wealth disparity (=wealthy and poor + の + difference) + は + get bigger/wider + just keeps on + です.”

So we had this phrase:

貧富の差は広がる
ひんぷ　の　さ　は　ひろがる
Wealth inequality increases
Literally: “wealth disparity (=wealthy and poor + の + difference) + は + get bigger/wider"

We snapped an 一方 onto the end of it, and the robots inside of Japanese people's brains changed the sentence's meaning to:

貧富の差は広がる一方です。
ひんぷ　の　さ　は　ひろがる　いっぽう　です。
Wealth inequality just continues to increase.
Literally: “wealth disparity (=wealthy and poor + の + difference) + は + get bigger/wider + just keeps on + です.”

Magic.

Or... science.

Same thing, right?

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👷 💀 Construction Destruction 💀 👷

This is cake. Just put V る right in front of 一方.

V る + 一方
just keeps on VERB-ing; just continues to VERB

Since 一方 means "one direction," it makes sense that this construction means "X's condition will continue to change in one direction."

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This is a great way to complain about all that fat you gained after having a baby:

子供を産んでから、私の体重は増える一方です。
こども　を　うんで　から、　わたし　の　たいじゅう　は　ふえる　いっぽう　です。
Since I had a baby, I’ve just been getting fatter and fatter.
Literally: “child + を + give birth to (and) + from, + I + の + weight + は + increase + just keeps on + です.”

I think you're allowed to use this excuse for your whole life after you have a baby, so you might want to learn it, especially if you have a uterus.

Also, complaining about your weight is a lot easier than dieting. This is good because with work/school and Japanese, your schedule is already pretty full.

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Yet another example:

雨宿りのために喫茶店に入ったが、雨は激しくなる一方だ。
あまやどり　の　ために　きっさてん　に　はいった　が、　あめ　は　はげしく　なる　いっぽう　だ。
I went into a coffee shop to avoid getting wet, but the rain just keeps getting worse.
Literally: “taking shelter from the rain + の + for the sake/purpose of + coffee shop + に + entered + but (=が), + rain + は + intense / violent + becomes + just keeps on + だ.”

I don't know why, but I love the word 雨宿り (あまやどり // taking shelter from rain). There's something just a bit romantic about it, yeah? Just chilling under an awning of some kind, watching water fall from the sky.

Water falling from the sky. How cool is that?

I've never met a Japanese person that likes rain--they all seem to hate it, but Tokyo is a wonderful place to get caught in the rain.

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Have you noticed that 一方 is used for negative things quite a bit?

Here's another one:

日本の景気はこれからも悪くなっていく一方だそうだ。
にほん　の　けいき　は　これから　も　わるく　なって　いく　いっぽう　だ　そうだ。
They say that Japan’s economy is just going to keep getting worse from now on.
Literally: “Japan + の + economic condition + は + from now / after this + also (=も) + bad + becomes (and) + just keeps on + だ + そうだ (=[hearsay marker]).”

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By the way, you could drop the だ・です after 一方 in casual spoken language.

Like this:

Textbook Casual / Stiff-Sounding Casual:
雨宿りのために喫茶店に入ったが、雨は激しくなる一方だ。
あまやどり　の　ために　きっさてん　に　はいった　が、　あめ　は　はげしく　なる　いっぽう　だ。
I went into a coffee shop to avoid getting wet, but the rain just keeps getting worse.
Literally: “taking shelter from the rain + の + for the sake/purpose of + coffee shop + に + entered + but (=が), + rain + は + intense / violent + becomes + just keeps on + だ.”

True Casual:
雨宿りのために喫茶店に入ったけど、雨は激しくなる一方。
あまやどり　の　ために　きっさてん　に　はいった　けど、　あめ　は　はげしく　なる　いっぽう。
I went into a coffee shop to avoid getting wet, but the rain just keeps getting worse.
Literally: “taking shelter from the rain + の + for the sake/purpose of + coffee shop + に + entered + but (=けど), + rain + は + intense / violent + becomes + just keeps on.”

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Another lesson finished. You're mastering Japanese 一方, fellow student.