Mastering I-Adjectives (い形容詞) for GCSE Japanese (1JA0)
Welcome to your complete revision guide for I-Adjectives! In GCSE Japanese, adjectives are essential for describing people, places, experiences, and food. Mastering how to change their endings, link them together, and turn them into adverbs will give you an immediate boost in Paper 2 (Speaking) and Paper 4 (Writing) under Knowledge and Application of Language.
Don't worry if Japanese adjective conjugations seem a little unusual at first. Unlike English adjectives, which stay the same (e.g. "it was cold"), Japanese i-adjectives change their own endings like little verbs. Let's break everything down step-by-step!
---1. Identifying I-Adjectives & The Golden Rule of いい
What is an I-Adjective?
True i-adjectives in their plain dictionary (present positive) form always end with the hiragana い (i).
• 大きい (ookii – big)
• 小さい (chiisai – small)
• 高い (takai – expensive/tall/high)
• 暑い (atsui – hot)
• 寒い (samui – cold)
• 楽しい (tanoshii – fun)
• おいしい (oishii – delicious)
The Adjective Stem
To change the form or tense of an i-adjective, you remove the final い. What remains is called the stem.
• \(\text{高い (takai)} - \text{い} = \text{高 (taka)}\)
• \(\text{寒い (samui)} - \text{い} = \text{寒 (samu)}\)
The Irregular Exception: いい (Good)
The word for "good" is いい (ii). However, when you change its tense or ending, it transforms back to its traditional stem: よい (yoi).
• Present: いい (plain) / いいです (polite)
• Negative: よくない (plain) / よくないです (polite)
• Past: よかった (plain) / よかったです (polite)
• Past Negative: よくなかった (plain) / よくなかったです (polite)
• Linking (Te-form): よくて
• Adverbial: よく / よくなる / よくする
Key Takeaway: Always drop the final い to find the stem before conjugating. Never say いくない or いかった—always use よく〜!
---2. Describing Nouns Directly (Attributive Form)
To describe a noun directly (like "red flower" or "delicious food"), simply place the adjective straight before the noun. You do not need any particle between them.
\(\text{Adjective (dictionary form)} + \text{Noun}\)
• 赤い花 (akai hana – a red flower)
• おいしい食べ物 (oishii tabemono – delicious food)
• 高い山 (takai yama – a tall mountain)
Past-Tense Descriptions with Nouns (Higher Tier)
You can also use the past plain form directly before a noun to describe what something was like:
• 楽しかった旅行 (tanashikatta ryokou – a trip that was fun / a fun trip)
• 寒かった日 (samukatta hi – a day that was cold)
Key Takeaway: Never put な (na) or の (no) between an i-adjective and a noun. It is directly attached: おいしいケーキ (correct), NOT *おいしいなケーキ.
---3. Sentence Endings & Tenses (Polite and Plain)
When an adjective comes at the end of a sentence (predicative use), it changes its ending based on tense and politeness level.
Foundation & Higher Conjugation Paradigm
1. Present Positive (It is...)
• Plain: [Stem] + い \(\rightarrow\) 高い (takai – It is expensive)
• Polite: [Stem] + いです \(\rightarrow\) 高いです (takai desu – It is expensive)
2. Present Negative (It is not...)
• Plain: [Stem] + くない \(\rightarrow\) 高くない (takanai – It is not expensive)
• Polite: [Stem] + くないです OR [Stem] + くありません \(\rightarrow\) 高くないです / 高くありません
3. Past Positive (It was...)
• Plain: [Stem] + かった \(\rightarrow\) 高かった (takakatta – It was expensive)
• Polite: [Stem] + かったです \(\rightarrow\) 高かったです (takakatta desu – It was expensive)
4. Past Negative (It was not...)
• Plain: [Stem] + くなかった \(\rightarrow\) 高くなかった (takanakatta – It was not expensive)
• Polite: [Stem] + くなかったです OR [Stem] + くありませんでした \(\rightarrow\) 高くなかったです / 高くありませんでした
The "Polite です" Rule
In polite i-adjective sentences, the word です is simply a politeness badge added at the very end. The adjective itself carries the tense. Therefore, です never changes to でした after an i-adjective!
• Correct: 赤かったです (It was red)
• Incorrect: *赤いでした (Wrong!)
Key Takeaway: To make a past polite sentence, turn the adjective into 〜かったです. Never use でした with an unconjugated i-adjective.
---4. Linking Adjectives: The 〜くて Form
When you want to list multiple qualities or give a reason in one fluent sentence, you use the linking 〜くて (-kute) form. This functions like the Japanese "and" or "and so" for adjectives.
\(\text{Stem} + \text{くて}\)
• 安い \(\rightarrow\) 安くて (cheap and...)
• 面白い \(\rightarrow\) 面白くて (interesting and...)
• いい \(\rightarrow\) よくて (good and...)
Function 1: Coordinating Qualities (Listing Traits)
Use 〜くて to connect descriptions that share the same overall positive or negative tone:
• この花は赤くてきれいです。 (Kono hana wa akakute kirei desu. – This flower is red and pretty.)
• 日本の電車は早くて、便利です。 (Nihon no densha wa hayakute, benri desu. – Japanese trains are fast and convenient.)
• 部屋は広くて、明るいです。 (Heya wa hirokute, akarui desu. – The room is spacious and bright.)
Function 2: Stating a Cause or Reason (Because / So)
The 〜くて form can also express a natural cause or reason for a result:
• 頭が痛くて、学校を休みました。 (Atama ga itakute, gakkou o yasumimashita. – My head hurt, so I was absent from school.)
• 寒くて、コートを着ました。 (Samukute, kouto o kimashita. – It was cold, so I put on a coat.)
Tip on Tone Matching: Linking with 〜くて connects ideas of similar polarity (positive + positive, or negative + negative). If you want to connect contrasting qualities, use が (ga) or けど (kedo) instead: 高いですが、おいしいです (It is expensive, but delicious).
Key Takeaway: Drop い and add くて to join adjectives smoothly and explain causes.
---5. Adverbs (〜く) and State Changes (〜くなる / 〜くする) [Higher Tier]
You can turn any i-adjective into an adverb to describe how an action is performed, or to show how things become or are made.
Formation of Adverbs: 〜く
\(\text{Stem} + \text{く} + \text{Verb}\)
• 早い (early/fast) \(\rightarrow\) 早く起きる (hayaku okiru – to wake up early)
• 大きい (big) \(\rightarrow\) 大きく書く (ookiku kaku – to write largely / write big)
• いい (good) \(\rightarrow\) よく勉強する (yoku benkyou suru – to study well / study hard)
Becoming: 〜くなる (Natural Change of State)
When something changes naturally or passively on its own, use 〜くなる (to become...). This structure uses the particle が or は with the subject.
\(\text{Stem} + \text{くなる}\)
• 寒くなりました。 (Samuku narimashita. – It became / got cold.)
• 背が高くなりました。 (Se ga takaku narimashita. – [He/She] got taller.)
• 天気がよくなりました。 (Tenki ga yoku narimashita. – The weather became good.)
Making / Causing: 〜くする (Intentional Change)
When an agent actively alters the state of something, use 〜くする (to make something...). Because you are doing this to an object, mark the object with を.
\(\text{Object} + \text{を} + \text{Stem} + \text{くする}\)
• 部屋を明るくします。 (Heya o akaruku shimasu. – I will make the room bright / turn on lights.)
• テレビの音を小さくしてください。 (Terebi no oto o chiisaku shite kudasai. – Please turn the TV volume down / make it smaller.)
• 字を大きく書きました。 (Ji o ookiku kakimashita. – I wrote the characters big.)
Key Takeaway: Use が 〜くなる for natural changes ("it gets cold") and を 〜くする for intentional actions ("I make it cold").
---6. Top Exam Pitfalls & Examiner Warnings
1. The "でした" Mistake
• Incorrect: *赤いでした / *おいしいでした
• Correct: 赤かったです / おいしかったです
Why? でした only attaches to nouns and na-adjectives. I-adjectives conjugate internally using 〜かったです.
2. The "Double Past" Mistake
• Incorrect: *高かったですした / *よかったですした
• Correct: 高かったです / よかったです
3. Forgetting the "いい \(\rightarrow\) よい" Rule
• Incorrect: *いくない / *いかった / *いくなる
• Correct: よくない / よかった / よくなる
4. Mixing up I-Adjectives and Na-Adjectives
• きれい (kirei – pretty/clean) and ゆうめい (yuumei – famous) end with the sound 'i', but they are Na-adjectives!
• Incorrect: *きれいかった / *きれいくない
• Correct: きれいでした / きれいじゃないです
5. Linking with で instead of くて
• Incorrect: *赤いで、きれいです
• Correct: 赤くて、きれいです (Use で only for na-adjectives and nouns!)
Quick Revision Summary Checklist
Before sitting your exam, make sure you can confidently check off each of these points:
• Direct noun modification requires no extra particle (高い山).
• Past polite is [Stem] + かったです.
• Present negative is [Stem] + くないです or [Stem] + くありません.
• いい always shifts to よい in negative, past, linking, and adverbial forms.
• Connect multiple adjectives using [Stem] + くて.
• Use 〜くなる for automatic changes (with が) and 〜くする for purposeful actions (with を).