～一方だ — Heading Ever Further In One Direction
Describes a situation that keeps changing steadily in a single direction, with no sign of stopping — things 'keep on' increasing, decreasing, worsening, etc. It conveys a continuous, one-way trend and often carries a nuance of concern when the trend is negative.
Structure
[Verb dictionary form] + 一方だ
Examples
物価は上がる一方だ。
Bukka wa agaru ippou da.
Prices just keep going up.
上がる (to rise) + 一方だ shows an unbroken upward trend with no sign of reversal.
彼の病気は悪くなる一方で、家族は心配している。
Kare no byouki wa waruku naru ippou de, kazoku wa shinpai shite iru.
His illness only keeps getting worse, and the family is worried.
悪くなる (to get worse) + 一方; here 一方で connects to a following clause.
田舎の人口は減る一方だ。
Inaka no jinkou wa heru ippou da.
The rural population just keeps declining.
減る (to decrease) + 一方だ expresses a continuous one-directional decline.
• Only attaches to the dictionary (plain non-past) form of verbs expressing change. • Often used for negative trends (worsening, rising costs), implying worry. • Do not confuse with 一方(で) meaning 'on the other hand'.
Commonly confused with
The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ～一方だ is tested against.
vs ばかりだ
～ばかりだ (as in 悪くなるばかりだ) is nearly synonymous but slightly more emotional/negative; 一方だ is more neutral about a steady trend.
vs つつある
つつある means a change is gradually in progress toward completion; 一方だ stresses an ongoing, unbroken direction with no endpoint implied.
More expressions
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