〜一方だ: 'Keeps Getting More and More'
What it means
〜一方だ describes a change that is moving steadily in a single direction and shows no sign of reversing. Think of it as English "keeps getting more and more ~" or "just keeps ~ing." The verb in front is almost always a change verb — 上がる, 増える, 悪くなる, 減る — something that names a trend rather than a one-off event.
Because it paints a one-way slide, it very often carries a negative or worrying feeling: things keep getting worse, busier, more expensive.
この町の人口は減る一方だ。
この まちの じんこうは へる いっぽうだ。
This town's population just keeps dropping.
減る (to decrease) is a change verb — perfect for 一方だ.
物価は上がる一方で、給料は変わらない。
ぶっかは あがる いっぽうで、きゅうりょうは かわらない。
Prices keep rising, while wages stay the same.
Here 上がる一方 stacks an escalating change with a contrast clause.
試験が近づいて、ヤッタンの不安は大きくなる一方だった。
しけんが ちかづいて、ヤッタンの ふあんは おおきく なる いっぽうだった。
As the exam drew near, Yattan's anxiety only grew and grew.
〜なる verbs (大きくなる) are textbook 一方だ material.
How to form it
Attach 一方だ directly to the dictionary (plain present) form of a verb. The verb should describe a change or trend.
| Element | Form | Example |
|---|---|---|
| Change verb (dictionary form) | Vる + 一方だ | 増える → 増える一方だ |
| 〜くなる / 〜になる | …なる + 一方だ | 悪くなる → 悪くなる一方だ |
| Past tense | 一方だった | 増える一方だった (kept increasing) |
| Polite | 一方です | 増える一方です |
Note: it always sits on the dictionary form — never 増えた一方だ, never 増えている一方だ. The verb itself stays plain present; the tense lives on だ/だった.
More examples
モチは新しい趣味を始めてから、出費が増える一方だ。
モチは あたらしい しゅみを はじめてから、しゅっぴが ふえる いっぽうだ。
Ever since Mochi took up a new hobby, his spending just keeps going up.
放っておくと、病人の容体は悪くなる一方ですよ。
ほうっておくと、びょうにんの ようたいは わるく なる いっぽうですよ。
If you leave it alone, the patient's condition will only get worse.
A typical warning use — the one-way change is undesirable.
先生によると、都会の人口は増える一方だそうだ。
せんせいに よると、とかいの じんこうは ふえる いっぽうだ そうだ。
According to the teacher, the urban population just keeps growing.
Common mistakes
- Confusing 一方だ with 一方(で). Same kanji, different jobs. 〜一方だ = an escalating one-way change (上がる一方だ = "keeps rising"). 〜一方(で) = a contrast, "on the other hand / while" (彼は厳しい一方で、優しいところもある = "he's strict, but also has a kind side"). If you can replace it with "more and more," it's 一方だ; if you can replace it with "whereas," it's 一方で.
- Using a non-change verb. 一方だ needs a verb that names a trend. 食べる一方だ or 見る一方だ sounds odd because those aren't directional changes. Reach for 増える, 減る, 上がる, 下がる, 悪くなる, 強くなる, and the like.
- Putting the verb in the past or 〜ている form. It's always the dictionary form: 悪くなる一方だ (✓), not 悪くなった一方だ (✗). Move the tense onto だ → だった instead.
- Forcing a positive nuance. While 一方だ can describe a good trend (成績は上がる一方だ), it most naturally fits worsening or unstoppable situations. If you just want a neutral "is increasing," 〜ている (増えている) is often more natural.
Quick recap
- 〜一方だ = a change that keeps going one way, more and more — often negative.
- Attach it to a dictionary-form change verb: 増える / 減る / 悪くなる + 一方だ.
- Tense rides on だ: 一方だ → 一方だった → 一方です.
- Don't mix it up with 〜一方(で) ("on the other hand"), which is a contrast.
Your turn
Pick the sentence that uses 〜一方だ correctly for a one-way change.
Start the 5-question drill →Frequently asked questions
What's the difference between 一方だ and 一方で?
〜一方だ at the end of a sentence means a change keeps intensifying in one direction (物価は上がる一方だ = 'prices keep rising'). 〜一方(で) joins two clauses to mean 'on the other hand / while' (厳しい一方で、優しい = 'strict, yet kind'). Same 一方, completely different use.
Which verb form comes before 一方だ?
The dictionary (plain present) form: 増える一方だ, 悪くなる一方だ. Never the past or 〜ている form. Tense is shown on だ → だった instead.
Does 一方だ always sound negative?
Not always, but usually. It most naturally describes worsening or unstoppable trends. It can describe a positive trend too (成績は上がる一方だ), but for a plain 'is increasing' the 〜ている form is often more neutral.
Can I use 一方だ with any verb?
Only with change/trend verbs — 増える, 減る, 上がる, 下がる, 〜くなる, 〜になる. Action verbs like 食べる or 見る don't work because they don't describe a one-directional change.