JLPT N4 Lesson 1: Plain Form Mastery

Master the plain (casual) forms of verbs, adjectives, and the copula to speak naturally with friends and lay the foundation for advanced N4 grammar structures.

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Overview

Welcome to your first step in JLPT N4! In N5, you primarily learned the polite form (teineigo), ending sentences with 〜ます (-masu) and 〜です (-desu). While polite form is essential for speaking with strangers, teachers, and superiors, the plain form (futsuukei / 普通形) is the true heartbeat of daily Japanese. It is the register used among close friends, family, and classmates.

More importantly, mastering the plain form is not just about "sounding casual." In N4 and beyond, almost all complex grammar structures—such as expressing thoughts (〜と思う), stating reasons (〜から), describing timing (〜とき), or expressing intentions (〜つもり)—require you to attach these patterns directly to the plain form. This lesson will systematically guide you through conjugating verbs, adjectives, and nouns into their plain present and past forms, and show you how to use them naturally in casual conversations.

Learning Objectives

By the end of this lesson you can:

  • Conjugate Group 1, 2, and 3 verbs into all four plain forms (present affirmative, present negative, past affirmative, and past negative).
  • Conjugate i-adjectives, na-adjectives, and nouns/copula into all four plain forms.
  • Distinguish when to use casual register (plain form) versus polite register (desu/masu) based on social context.
  • Apply casual sentence-final particles (よ, ね, じゃん, だよ) naturally in casual conversations.

New Vocabulary

Japanese Reading Romaji English Part of Speech
行く いく iku to go Verb (Group 1)
食べる たべる taberu to eat Verb (Group 2)
来る くる kuru to come Verb (Group 3)
する する suru to do Verb (Group 3)
面白い おもしろい omoshiroi interesting, funny I-adjective
暇 ひま hima free, not busy Na-adjective
友達 ともだち tomodachi friend Noun
明日 あした ashita tomorrow Noun
美味しい おいしい oishii delicious I-adjective
宿題 しゅくだい shukudai homework Noun
映画 えいが eiga movie Noun
遊ぶ あそぶ asobu to play, hang out Verb (Group 1)
忙しい いそがしい isogashii busy I-adjective
雨 あめ ame rain Noun
喋る しゃべる shaberu to chat, talk Verb (Group 1)
じゃん じゃん jan isn't it? (casual) Particle

Grammar Points

1. Verb Plain Forms (The Four Quadrants)

Structure:

  • Present Affirmative: Dictionary Form (e.g., 書く / 食べる / する)
  • Present Negative: 〜ない Form (e.g., 書かない / 食べない / しない)
  • Past Affirmative: 〜た Form (e.g., 書いた / 食べた / した)
  • Past Negative: 〜なかった Form (e.g., 書かなかった / 食べなかった / しなかった)

To master plain form verbs, you must categorize them into their three respective groups. Group 1 (U-verbs) change their final vowel sound. Group 2 (Ru-verbs) drop the final 〜る (-ru). Group 3 (Irregular) consists of する (suru) and 来る (kuru).

The past negative is formed by taking the present negative (〜ない), dropping the final 〜い, and adding 〜かった (-katta).

Japanese Reading Romaji English
明日、京都に行く。 あした、きょうとにいく。 Ashita, Kyōto ni iku. I will go to Kyoto tomorrow.
今日は朝ご飯を食べない。 きょうはあさごはんをたべない。 Kyō_wa asagohan o tabenai. I won't eat breakfast today.
昨日、友達と遊んだ。 きのう、ともだちとあそんだ。 Kinō, tomodachi to asonda. I hung out with my friend yesterday.
先週、宿題をしなかった。 せんしゅう、しゅくだいをしなかった。 Senshū, shukudai o shinakatta. I didn't do my homework last week.

Common mistake: ❌ 食べないでした (tabenai deshita) → ✓ 食べなかった (tabenakatta) — Do not combine the plain negative form with the polite past copula "deshita" in casual speech.

2. Adjective and Copula (Noun) Plain Forms

Structure:

  • I-Adjectives:
    • Present Affirmative: [Adjective] (e.g., 美味しい)
    • Present Negative: 〜くない (e.g., 美味しくない)
    • Past Affirmative: 〜かった (e.g., 美味しかった)
    • Past Negative: 〜くなかった (e.g., 美味しくなかった)
  • Na-Adjectives & Nouns (Copula):
    • Present Affirmative: 〜だ (e.g., 暇だ / 友達だ)
    • Present Negative: 〜じゃない (e.g., 暇じゃない / 友達じゃない)
    • Past Affirmative: 〜だった (e.g., 暇だった / 友達だった)
    • Past Negative: 〜じゃなかった (e.g., 暇じゃなかった / 友達じゃなかった)

Unlike verbs, adjectives and nouns have distinct conjugation patterns. Note that for i-adjectives, you simply drop the polite です (desu) to make them plain. For na-adjectives and nouns, the polite です (desu) becomes だ (da) in the plain present affirmative.

Japanese Reading Romaji English
この映画は面白い。 このえいがはおもしろい。 Kono eiga wa omoshiroi. This movie is interesting.
テストは難しくなかった。 てすとはむずかしくなかった。 Tesuto wa muzukashikunatta. The test wasn't difficult.
明日は暇だ。 あしたはひまだ。 Ashita wa hima da. I am free tomorrow.
昨日は雨じゃなかった。 きのうはあめじゃなかった。 Kinō wa ame janakatta. Yesterday was not rainy (It didn't rain yesterday).

Common mistake: ❌ 美味しいだ (oishii da) → ✓ 美味しい (oishii) — Never add "da" directly after an i-adjective in the plain form.

3. Casual Sentence-Final Particles (よ, ね, じゃん, だよ)

Structure:

  • Plain Form + よ / ね (e.g., 行くよ / 暇だね)
  • Noun / Na-Adjective + だよ (e.g., 友達だよ / 暇だよ)
  • Plain Form + じゃん (e.g., 美味しいじゃん / 行くじゃん)

In casual speech, sentence-final particles add nuance, emotion, and soft tones.

  • よ (yo) asserts new information or emphasis.
  • ね (ne) seeks agreement (like "isn't it?").
  • だよ (da yo) is used with nouns and na-adjectives to make the assertion sound softer and friendlier than just using だ (da).
  • じゃん (jan) is a highly casual contraction of じゃないか (janai ka), used to mean "isn't it?" or "right?" when pointing out something obvious.
Japanese Reading Romaji English
このケーキ、すごく美味しいよ！ このけーき、すごくいしいよ！ Kono kēki, sugoku oishii yo! This cake is really delicious, you know!
明日は休みだね。 あしたはやすみだね。 Ashita wa yasumi da ne. Tomorrow is a holiday, isn't it?
今日は忙しいんだよ。 きょうはいそがしいんだよ。 Kyō wa isogashii n da yo. I'm busy today, you see.
日本語、上手じゃん！ にほんご、じょうずじゃん！ Nihongo, jōzu jan! Your Japanese is really good, isn't it!

Common mistake: ❌ 暇よ (hima yo) → ✓ 暇だよ (hima da yo) — When ending a sentence with a noun or na-adjective in casual speech, you must include "da" before "yo" or "ne" to sound natural (unless you are using feminine speech patterns).

Dialogues

Dialogue 1: Planning the Weekend

Two university classmates, Sora and Yuka, are talking after class about their weekend plans.

Sora: Yuka, ashita wa hima?
Sora: ゆうか、あしたはひま？
Sora: 裕香、明日は暇？
English: Yuka, are you free tomorrow?

Yuka: Un, ashita wa nani mo yotei ga nai yo. Sora wa?
Yuka: うん、あしたはなにもよていがないよ。そらは？
Yuka: うん、明日は何も予定がないよ。空は？
English: Yeah, I don't have any plans tomorrow. What about you, Sora?

Sora: Atarashii eiga o mini ikanai? Omoshiroi yo.
Sora: あたらしいえいがをみにいかない？おもしろいよ。
Sora: 新しい映画を見に行かない？面白いよ。
English: Won't you go see a new movie with me? It's interesting, you know.

Yuka: Ii ne! Nani o miru no?
Yuka: いいね！なにをみるの？
Yuka: いいね！何を見るの？
English: Sounds good! What are we going to watch?

Sora: Anime no eiga da yo. Kinō hajimatta jan?
Sora: あにめのえいがだよ。きのうはじまったじゃん？
Sora: アニメの映画だよ。昨日始まったじゃん？
English: It's an anime movie. It started yesterday, didn't it?

Yuka: Ah, are ne! Zehi ikitai!
Yuka: あ、あれね！ぜひいきたい！
Yuka: あ、あれね！ぜひ行きたい！
English: Oh, that one! I'd love to go!

Dialogue 2: Talking About Yesterday's Party

Ken and Hana, close coworkers of the same age, chat during their lunch break.

Ken: Hana, kinō no pāti ni kita?
Ken: はな、きのうのぱーてぃにきた？
Ken: 花、昨日のパーティーに来た？
English: Hana, did you come to yesterday's party?

Hana: Uun, ikanakatta. Shigoto ga isogashikatta kara.
Hana: ううん、いかなかった。しごとがいそがしかったから。
Hana: ううん、行かなかった。仕事が忙しかったから。
English: No, I didn't go. Because my work was busy.

Ken: Sō datta n da. Zannen. Pāti, sugoku tanoshikatta yo.
Ken: そうだったんだ。ざんねん。ぱーてぃ、すごくたのしかったよ。
Ken: そうだったんだ。残念。パーティー、すごく楽しかったよ。
English: Ah, I see. That's too bad. The party was really fun, you know.

Hana: Dare ga kita no?
Hana: だれがきたの？
Hana: 誰が来たの？
English: Who came?

Ken: Tanaka-san to Yamada-san ga kita yo. Suzuki-san wa konakatta.
Ken: たなかさんとやまださんがきたよ。すずきさんはこなかった。
Ken: 田中さんと山田さんが来たよ。鈴木さんは来なかった。
English: Tanaka and Yamada came. Suzuki didn't come.

Hana: Sō jan. Tsugi wa zettai iku ne!
Hana: そうじゃん。つぎはぜったいいくね！
Hana: そうじゃん。次は絶対行くね！
English: Ah, is that so. I'll definitely go next time!

Grammar Drills

Exercise 1: Fill in the blank (Conjugate the word in parentheses into the appropriate casual plain form based on the context)

  1. 明日、一緒に図書館に (行く) ________？ (hint: invitation/present negative)
  2. 昨日のテストは全然 (難しい) ________。 (hint: past negative)
  3. このスープ、とても (美味しい) ________ よ！ (hint: present affirmative)
  4. 去年、京都は (雨だ) ________。 (hint: past affirmative)
  5. 彼は私の (友達だ) ________ じゃない。 (hint: present negative)
  6. 昨日、宿題を (する) ________ から、今日は暇だよ。 (hint: past affirmative)
  7. その映画、全然 (面白い) ________ なかった。 (hint: past negative)
  8. 明日は日曜日 (だ) ________ ね。 (hint: present affirmative copula)
  9. 彼女は昨日、学校に (来る) ________。 (hint: past negative)
  10. 一緒にゲームを (する) ________ よ！ (hint: present affirmative / invitation)

Answer Key:

  1. 行かない (ikanai)
  2. 難しくなかった (muzukashikunatta)
  3. 美味しい (oishii)
  4. 雨だった (ame datta)
  5. 友達 (tomodachi)
  6. した (shita)
  7. 面白く (omoshiroku)
  8. だ (da)
  9. 来なかった (konakatta)
  10. する (suru)

Translation Practice

English → Japanese (Translate these sentences using plain form):

  1. I didn't eat lunch yesterday.
  2. This book wasn't very interesting.
  3. Tomorrow is a holiday, right? (using casual particles)
  4. Did you hang out with your friend yesterday?
  5. My homework wasn't difficult.

Japanese → English (Translate these sentences into natural English): 6. 明日、学校に行く？ (あした、がっこうにいく？ / Ashita, gakkō ni iku?) 7. 昨日は暇じゃなかったよ。 (きのうはひまじゃなかったよ。 / Kinō wa hima janakatta yo.) 8. そのケーキ、美味しかったじゃん！ (そのけーき、おいしかったじゃん！ / Sono kēki, oishikatta jan!) 9. 宿題をしなかった。 (しゅくだいをしなかった。 / Shukudai o shinakatta.) 10. 今日は雨だね。 (きょうはあめだね。 / Kyō wa ame da ne.)

Answer Key:

  1. 昨日、昼ご飯を食べなかった。 (きのう、ひるごはんをたべなかった。 / Kinō, hirugohan o tabenakatta.)
  2. この本はあまり面白くなかった。 (このほんはあまりおもしろくなかった。 / Kono hon wa amari omoshirokunatta.)
  3. 明日は休みだね。 (あしたはやすみだね。 / Ashita wa yasumi da ne.)
  4. 昨日、友達と遊んだ？ (きのう、ともだちとあそんだ？ / Kinō, tomodachi to asonda?)
  5. 宿題は難しくなかった。 (しゅくだいはむずかしくなかった。 / Shukudai wa muzukashikunatta.)
  6. Are you going to school tomorrow?
  7. I wasn't free yesterday, you know.
  8. That cake was delicious, wasn't it!
  9. I didn't do my homework.
  10. It's raining today, isn't it?

Cultural Note

In Japanese society, the distinction between Uchi (inside/in-group) and Soto (outside/out-group) dictates which linguistic register you must use. Plain form (futsuugo) is reserved exclusively for your Uchi circle—family, close friends, peers of the same age, or those younger than you.

Using plain form with a superior, a stranger, or a teacher is considered highly inappropriate and rude, as it prematurely breaks the social distance required by Japanese etiquette. Conversely, using polite form (teineigo) with your close friends can make you sound cold, distant, and overly formal, as if you are intentionally keeping them at arm's length. Learning when to switch between these registers is a vital social skill in Japan.

Self-Check

Answer these questions to verify your understanding:

  1. What is the plain past negative form of the verb 食べる (taberu)?
  2. Why is it incorrect to say "美味しいだ" (oishii da)?
  3. How do you change a na-adjective like 暇 (hima) into the plain past affirmative?
  4. What nuance does the casual particle じゃん (jan) add to a sentence?
  5. In what social situations should you avoid using the plain form?