Mastering い-Adjectives (I-Kiyoushi) | JLPT N5 Grammar

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Mastering い-Adjectives (I-Kiyoushi) | JLPT N5 Grammar
Meaning & Usage

✨ Basic Meaning

い-adjectives (形容詞 / keiyōshi) are true adjectives in Japanese that always end in the hiragana ‘い’. They are used to describe qualities, states, or characteristics of a noun.

🎯 Primary Function

To describe a noun or function as the predicate of a sentence, expressing a quality or state.

📋 Grammar Structure

い-adjective + です (Polite Predicate Form)
い-adjective + Noun (Attributive Form)
Noun + は + い-adjective + です (Polite Predicate Sentence Structure)
い-adjective (drop い) + くないです (Polite Negative)

🎭 Usage Contexts

🏢 Formal Situations

Used with です for polite/formal settings (e.g., 寒いです). Conjugations must be polite.

😊 Informal Situations

Used in their plain form (without です) when speaking to close friends or family (e.g., 寒い).

✍️ Written Language

Used formally in polite writing with です, or in plain form in essays, stories, or textbook definitions.

🗣️ Spoken Language

Very common in all spoken contexts, often followed by です or conversational particles.

💡 Common Applications

Modifying Nouns
The adjective comes directly before the noun it modifies, without any connecting particles like な (unlike Na-adjectives).
Example: 美味しいご飯 (Oishii gohan)
Serving as a Predicate (Polite)
In polite speech, the i-adjective stands at the end of the sentence and is followed by です. The ‘い’ remains.
Example: このケーキは甘いです。(Kono kēki wa amai desu.)
Forming Negative and Past Tenses
I-adjectives are conjugated by dropping the final ‘い’ and adding suffixes (e.g., -くない for negative, -かった for past).
Example: 楽しくない (Tanoshikunai) / 暑かった (Atsukatta)
📊
Frequency
Extremely High
🎚️
Difficulty
Easy (N5 Foundational)
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Related Kanji

JLPT N5 Kanji List

Related Vocabulary

JLPT N5 Vocabulary List
Example Sentences
Example #1
このアパートは狭いです。
Furigana: このアパートはせまいです。
Romaji: Kono apāto wa semai desu.
English: This apartment is narrow.
Example #2
古い本を読みました。
Furigana: ふるいほんをよみました。
Romaji: Furui hon o yomimashita.
English: I read an old book.
Example #3
昨日の試験は難しくなかったです。
Furigana: きのうのしけんはむずかしくなかったです。
Romaji: Kinō no shiken wa muzukashikunakatta desu.
English: Yesterday’s test was not difficult.
Example #4
あの店は安くて、美味しいです。
Furigana: あのみせはやすくて、おいしいです。
Romaji: Ano mise wa yasukute, oishii desu.
English: That restaurant is cheap and delicious.
Example #5
富士山は高い山です。
Furigana: ふじさんはたかいやまです。
Romaji: Fujisan wa takai yama desu.
English: Mt. Fuji is a tall mountain.
Example #6
寒いから、コートを着てください。
Furigana: さむいから、コートをきてください。
Romaji: Samui kara, kōto o kite kudasai.
English: Since it is cold, please put on a coat.
Example #7
そのカバンは重いですか。
Furigana: そのカバンはおもいですか。
Romaji: Sono kaban wa omoi desu ka.
English: Is that bag heavy?
Example #8
いい友達がたくさんいます。
Furigana: いいともだちがたくさんいます。
Romaji: Ii tomodachi ga takusan imasu.
English: I have many good friends.
Example #9
今日の天気は良くないです。
Furigana: きょうのてんきはよくないです。
Romaji: Kyō no tenki wa yokunai desu.
English: Today’s weather is not good.
Example #10
この仕事は忙しいですが、楽しいです。
Furigana: このしごとはいそがしいですが、たのしいです。
Romaji: Kono shigoto wa isogashii desu ga, tanoshii desu.
English: This job is busy, but it is fun.
Notes & Nuances

📌 Important Points

The Exception: 良い (よい / いい)
The adjective 良い (よい) or いい (ii) is the only exception. While it is often pronounced/written as いい, its conjugational root is 良く (yoku), derived from the original form 良い (よい). Always use 良くない or 良かった.
Example: いいです (ii desu) / 良くないです (yokunai desu)
Direct Modification Rule
When an i-adjective modifies a noun, it directly precedes the noun without any intervening particles (like the な required for na-adjectives).
Example: 大きい家 (Ōkii ie) / 小さい猫 (Chiisai neko)

⚠️ Common Mistakes

❌ 寒い**い**です。 / 寒**です**。 (Samuiidesu. / Samudesu.)
✅ 寒い**です**。 (Samui desu.)
The final ‘い’ of the adjective must *not* be dropped before adding です. Only drop ‘い’ when conjugating for negative or past tense.
❌ 新しい**じゃありません**。 (Atarashii ja arimasen.)
✅ 新し**くない**です。 (Atarashikunai desu.)
Do not use the particle じゃありません / ではありません (which is for nouns and Na-adjectives). I-adjectives have their own negative conjugation.

🏛️ Cultural Context

Politeness Level: Medium. The base form is plain, but adding です elevates the politeness to the standard polite level used in most public interactions (です/ます form).
Social Situations: Use the plain form when speaking to people of equal or lower status in casual settings, and the です form when speaking to superiors, strangers, or in professional settings.
Regional Variations: Standard forms are universally understood, but regional dialects may use different particles or endings in informal speech (e.g., very informal Osaka-ben might use 寒いで in some contexts, but this is advanced and specific).

🔍 Subtle Differences

い-adjectives vs. な-adjectives
い-adjectives conjugate themselves and end in い. な-adjectives do not conjugate themselves and require the particle な to modify nouns (e.g., きれいな花).
When to use: Use い-adjectives for inherent qualities (e.g., size, color, temperature). Use な-adjectives for descriptive states or qualities often related to appearance or feeling (though this distinction is not absolute).

📝 Conjugation Notes

I-adjectives are unique because they inflect (conjugate) themselves. The conjugation stem is formed by dropping the final ‘い’. * **Plain Past Positive:** drop い + かった (e.g., 寒かった) * **Plain Past Negative:** drop い + くなかった (e.g., 寒くなかった) * **Polite forms** are created by adding です after the plain conjugated form (e.g., 寒かったです, 寒くないです).

🔊 Pronunciation Tips

When an i-adjective is followed by です (e.g., 寒いです), the ‘い’ in です is often whispered or dropped in casual speech, making it sound like ‘samui des.’

🧠 Memory Tips

Remember the rule: ‘I have to take the I out to conjugate.’ Think of the ‘い’ as the trigger for the change. If you are describing the quality *now* (present positive), the ‘い’ stays. If you change the tense or polarity, the ‘い’ goes and is replaced by a suffix.

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