Meaning & Usage
✨ Basic Meaning
“To be continuously/steadily increasing or decreasing”; “to be getting more and more.”
🎯 Primary Function
To indicate that a situation or state is steadily and persistently moving in a single direction (e.g., only getting better, only getting worse).
📋 Grammar Structure
V-dictionary form (Vる) + 一方だ
I-Adjective stem + くなる + 一方だ (e.g., 高くなる一方だ)
Na-Adjective stem + になる + 一方だ (e.g., 深刻になる一方だ)
V-dictionary form + 一方だ (often used with verbs expressing decrease or decline, e.g., 減る一方だ)
🎭 Usage Contexts
Formal Situations
Highly appropriate. Used in business, academic papers, and official reports.
Informal Situations
Less common, as it sounds too formal for casual conversation, but is understood.
Written Language
Very common in essays, newspapers, reports, and informational texts.
Spoken Language
Used in formal speeches, news broadcasts, and serious conversations.
💡 Common Applications
Describing Socio-Economic Trends
Used frequently in news, reports, and formal discussions to describe persistent, unidirectional changes in statistics, economics, or social conditions.
Example: 最近の経済状況は悪くなる一方だ。
Discussing Personal Situations (Health, Skill, etc.)
Applicable to personal changes, often emphasizing a sustained positive or negative trend over time. (Note: Negative trends are more common.)
Example: 彼の日本語は上達する一方だ。
Environmental and Global Issues
Used to highlight ongoing, critical changes in the environment or global political landscape.
Example: 地球の自然環境は破壊される一方だ。
Frequency
Moderately frequent in formal and written contexts.
Difficulty
JLPT N3 / N2 Transition
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Example Sentences
Example #1
日本の人口は減る一方だ。
Furigana: にほんのじんこうはへるいっぽうだ。
Romaji: Nihon no jinkō wa heru ippō da.
English: Japan’s population is continuously decreasing.
Example #2
最近、物価が上がる一方だ。
Furigana: さいきん、ぶっかがあがるいっぽうだ。
Romaji: Saikin, bukka ga agaru ippō da.
English: Recently, commodity prices are steadily rising.
Example #3
彼は病気になってから、体重が減る一方だ。
Furigana: かれはびょうきになってから、たいじゅうがへるいっぽうだ。
Romaji: Kare wa byōki ni natte kara, taijū ga heru ippō da.
English: Since he got sick, his weight has been continuously dropping.
Example #4
地球温暖化の問題は深刻になる一方だ。
Furigana: ちきゅうおんだんかのもんだいはしんこくになるいっぽうだ。
Romaji: Chikyū ondanka no mondai wa shinkoku ni naru ippō da.
English: The problem of global warming is getting more serious all the time.
Example #5
スマートフォン依存症の人は増える一方だと言われている。
Furigana: スマートフォンいそんしょうのひとはふえるいっぽうだといわれている。
Romaji: Sumātofon isonshō no hito wa fueru ippō da to iwarete iru.
English: It is said that the number of people addicted to smartphones is steadily increasing.
Example #6
二人の関係は、時間が経つにつれて悪くなる一方だった。
Furigana: ふたりの関係は、じかんがたつにつれてわるくなるいっぽうだった。
Romaji: Futari no kankei wa, jikan ga tatsu ni tsurete waruku naru ippō datta.
English: The relationship between them was continuously worsening as time went on.
Example #7
インターネットの利用者は世界中で増える一方だ。
Furigana: インターネットのりようしゃはせかいじゅうでふえるいっぽうだ。
Romaji: Intānetto no riyōsha wa sekaijū de fueru ippō da.
English: The number of internet users is continuously increasing all over the world.
Example #8
技術の進歩は速くなる一方なので、追いつくのが大変だ。
Furigana: ぎじゅつのしんぽははやくなるいっぽうなので、おいつくのがたいへんだ。
Romaji: Gijutsu no shinpo wa hayaku naru ippō na node, oitsuku no ga taihen da.
English: Technological progress is getting faster and faster, so it’s hard to keep up.
Example #9
円安の影響で、海外旅行の費用は高くなる一方だ。
Furigana: えんやすのえいきょうで、かいがいりょこうのひようはたかくなるいっぽうだ。
Romaji: En’yasu no eikyō de, kaigai ryokō no hiyō wa takaku naru ippō da.
English: Due to the weak yen, the cost of overseas travel is continuously getting higher.
Example #10
彼の学業成績は最近落ちる一方だ。
Furigana: かれのがくぎょうせいせきはさいきんおちるいっぽうだ。
Romaji: Kare no gakugyō seiseki wa saikin ochiru ippō da.
English: His academic performance has been declining lately.
Notes & Nuances
📌 Important Points
Emphasizes Unidirectional and Continuous Change.
The pattern strongly emphasizes that the change is steady and uninterrupted, heading in a single direction without leveling off or reversing.
Example: 彼は病気が悪くなる一方だ。
Commonly Used for Negative Trends.
While it can describe both positive (上達する) and negative (減る) trends, it is statistically more often used to express concern about worsening or undesirable situations.
Example: 環境破壊は進む一方だ。 (Environmental destruction is advancing.)
Focuses on Long-Term Trends.
The structure is mainly used for observations about ongoing states or trends, not short-term fluctuations or one-time events. It implies a long-term pattern.
Example: 日本の経済は回復する一方だ。
⚠️ Common Mistakes
❌ Using the Vた (past) form.
✅ 日本の人口は減った一方だ。 (Nihon no jinkō wa hetta ippō da.)
The grammar must attach to the dictionary form (Vる) to denote a continuous action or trend, not the past tense (Vた).
❌ Attaching directly to an I-adjective (e.g., 高い一方だ).
✅ このスマホは高いいっぽうだ。 (Kono sumaho wa takai ippō da.)
Adjectives must be converted into a verb phrase using ‘なる’ (to become) before attaching to 一方だ.
❌ Using it for intended, momentary actions.
✅ 私たちは努力をする一方だ。 (Watashitachi wa doryoku o suru ippō da.)
While grammatically correct, 一方だ is typically used to describe situations *outside of one’s direct, momentary control* or a natural flow, rather than an intentional, willed action.
🏛️ Cultural Context
Politeness Level: Neutral to Formal. Its usage elevates the tone of the statement, making it suitable for objective analysis.
Social Situations: Best used when analyzing a continuous trend, expressing concern about a negative situation, or providing factual reports.
Regional Variations: Standard Japanese; no significant regional variations in usage or meaning.
🔍 Subtle Differences
〜一方だ vs. 〜ばかりだ
一方だ indicates that the situation *has been* continuously changing. ばかりだ often implies that the situation is *only* moving in that direction and suggests anticipation or immediate change (though they are sometimes interchangeable).
When to use: Use 一方だ for established, ongoing, long-term trends. Use ばかりだ when the trend has recently begun or is about to accelerate.
〜一方だ vs. 〜ていく
〜ていく simply describes a movement continuing into the future (e.g., 悪くなっていく). 一方だ is more formal and strongly emphasizes the lack of deviation from the trend.
When to use: Use 一方だ for formal, analytical statements about a persistent trend. Use 〜ていく for a more general description of future continuity.
📝 Conjugation Notes
The pattern strictly requires the Dictionary Form (Vる). Even nouns and adjectives must be conjugated into a Vる phrase (e.g., Noun + になる, Adj + くなる) before attaching 一方だ. It never attaches to Vます, Vた, or Noun/Adjective stems directly.
🔊 Pronunciation Tips
Pronounce ‘いっぽうだ’ with a strong emphasis on the double ‘p’ sound (促音 – sokuon). The tone is flat, making it sound objective.
🧠 Memory Tips
Think of ‘一方’ (one direction/one side) literally: the situation is moving only in that single direction (up or down). The ‘だ’ adds the declarative, factual tone.
Other Grammar
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