The plain form

The beginner course taught every verb in its ます form, which is polite, correct, and unable to appear anywhere in a sentence except right at the end. That single restriction is what stops a learner at the end of a beginner course from saying anything longer than one clause, and lifting it is the entire business of this lesson.

What ます cannot do

ます is not part of the verb. It is a suffix bolted on to mark politeness towards the person you are speaking to, and Japanese attaches it exactly once, to the last verb of the sentence. You have already seen this and may not have noticed. In 朝あさごはんを食たべて、学校がっこうに行いきます, there are two verbs and only one of them is polite. The first is in the て form, which carries no politeness and no tense, and the second decides both for the whole sentence.

Every other structure in Japanese behaves the same way, and this is where the beginner's vocabulary runs out. To say "the book I bought", "before I eat", "because it rained", "I think he came", "if you go", each of those inner verbs sits inside the sentence rather than at the end of it, so none of them can wear ます. They all take the plain form, and until you can build it on demand none of those sentences is available to you. 「買かいました本ほん」 is not a slightly informal way of saying "the book I bought". It is not Japanese at all.

This is why the plain form deserves a lesson of its own rather than a paragraph in a chapter on casual speech. Textbooks that introduce it as "the casual form" mislead badly, because they suggest it is an alternative you may decline. It is the base form of the verb, the shape everything else is built from, and the fact that it also serves as casual speech when it happens to land at the end of a sentence is a second job it does on the side. That second job is real, and the last lesson of this course is about it. For the next fourteen lessons the plain form is grammar, not register, and you can build every structure ahead of you while speaking as politely as you like.

There is one number worth holding on to. Written Japanese defaults to plain: novels, newspapers, academic papers, most signage and the great majority of what is on the internet end their sentences in the plain form, and reserve ます for dialogue and letters. A reader who knows only ます can speak politely and read almost nothing.

The dictionary form

The dictionary form is the headword, the shape a verb is listed under, and it is the one you build everything else from. You already know the ます form of a few dozen verbs, so the fastest route is to convert.

Group 2 verbs, the ones whose ます form has an え or い sound belonging to the stem, simply take る. 食たべます becomes 食たべる, 見みます becomes 見みる, 起おきます becomes 起おきる, 教おしえます becomes 教おしえる.

Group 3 has its two members and they are irregular as always. します becomes する, and 来きます becomes 来くる, which is worth saying aloud a few times because the reading of the character changes with the form.

Group 1 is the interesting one. Strip ます and you are left with a stem whose last kana is always in the い row: かい, まち, かえり, のみ, あそび, きき, いそぎ, はなし. Move that kana one step to the う row of the same column and you have the dictionary form.

Nine rows, and they are all of them. Every group 1 verb in the language ends its dictionary form in one of う, つ, る, む, ぶ, ぬ, く, ぐ or す, which is why the て form you drilled last course needed only five rules: う, つ and る collapse into って, む, ぶ and ぬ collapse into んで, and く, ぐ and す take one row each. Three plus three plus one plus one plus one accounts for all nine. 死しぬ is worth a note of its own, because it is the only ぬ verb in ordinary modern Japanese, which means the んで row is carried almost entirely by む and ぶ.

Now the honest limit. Converting from ます to dictionary form always works, because the ます form tells you the group by construction. Converting the other way does not. 食たべる is group 2 and 帰かえる is group 1, and nothing in the written shape distinguishes them. Verbs that end in いる or える and are nonetheless group 1 are a small but very common set: 帰かえる, 切きる, 入はいる, 走はしる, 知しる, 要いる, 限かぎる. Learn a verb with its group attached, exactly as you learn a noun with its counter.

Example. Give the dictionary forms of 持もちます (group 1), 降ふります (group 1), 借かります (group 2) and 呼よびます (group 1).

Take the group 1 verbs first and move the stem's last kana to the う row. 持もちます has stem 持もち, so ち goes to つ: 持もつ. 降ふります has stem 降ふり, so り goes to る: 降ふる. 呼よびます has stem 呼よび, so び goes to ぶ: 呼よぶ. 借かります is the trap and the reason it was included: its stem also ends in り, but it is group 2, so it takes る directly and gives 借かりる, not 借かる. The written result differs by one kana and the group is the only thing that decides it.

Now you. Give the dictionary forms of 立たちます (group 1), 開あけます (group 2), 泳およぎます (group 1) and 走はしります (group 1).

The ない form

The plain negative ends in ない, and the rule is stated most cleanly from the dictionary form: replace the final う-row kana with the あ-row kana in the same column, then add ない.

飲のむ gives 飲のまない. 待まつ gives 待またない. 帰かえる gives 帰かえらない. 聞きく gives 聞きかない. 急いそぐ gives 急いそがない. 話はなす gives 話はなさない. 遊あそぶ gives 遊あそばない.

There is one exception, and it is systematic rather than random. Verbs ending in う do not go to あ but to わ, so 買かう gives 買かわない and not 買かあない. The historical reason is that the わ was there all along: these verbs ended in an old は-row consonant that survived only before あ. The practical reason to remember it is that う verbs are extremely common, so getting it wrong is expensive: 言いわない, 使つかわない, 歌うたわない, 会あわない.

Group 2 drops る and adds ない: 食たべない, 見みない, 起おきない. Group 3 gives しない and 来こない, and note again that the reading of 来くる shifts, to こ this time.

Then there is ある, to exist for inanimate things, whose plain negative is not あらない but simply ない. This is the single most irregular thing in the ordinary verb system and it is unavoidable, because ある is one of the commonest verbs in the language. 時間じかんがない means there is no time. Its polite form, ありません, is perfectly regular, which is why beginners never meet the problem.

The plain past, free of charge

The plain past is the one place where a course can hand you a whole tense for nothing. Take the て form and change て to た, or で to だ. That is the entire rule, for all three groups, with no exceptions at all.

買かって becomes 買かった. 飲のんで becomes 飲のんだ. 聞きいて becomes 聞きいた. 急いそいで becomes 急いそいだ. 話はなして becomes 話はなした. 食たべて becomes 食たべた. して becomes した. 来きて becomes 来きた. And 行いく, which was the one exception in the て form, keeps the same exception: 行いって gives 行いった.

If your て forms are automatic, your past forms are already automatic. If they are not, the た form gives you a second reason to fix that today, and the same five rows do both jobs.

The plain negative past is equally cheap. Every ない form is an い adjective in disguise: it ends in い, it takes くて to join clauses, and it makes its past the way 高たかい makes 高たかかった. So drop the い of ない and add かった.

買かわない gives 買かわなかった. 食たべない gives 食たべなかった. 来こない gives 来こなかった. ない itself gives なかった, so 時間じかんがなかった means there was no time.

Example. Give all four plain forms of 書かく.

The dictionary form is 書かく, given. The negative replaces く with か and adds ない: 書かかない. The past comes from the て form, and く takes the いて row, so 書かいて gives 書かいた. The negative past takes the negative and swaps い for かった: 書かかなかった. Set against the polite four, 書かきます, 書かきません, 書かきました, 書かきませんでした, the pairing is exact: four plain forms, four polite ones, the same four meanings.

Now you. Give all four plain forms of 待まつ, and all four of 来くる.

Adjectives, nouns and だ

Verbs are not the only thing that has to shed です in the middle of a sentence, and adjectives turn out to be the easy half.

An い adjective was never polite to begin with. 高たかい is already plain, and its four forms are the ones you learned last course with the です simply removed: 高たかい, 高たかくない, 高たかかった, 高たかくなかった. The one irregular member is いい, good, which borrows every form except the plain present from its older shape よい: いい, よくない, よかった, よくなかった. There is no such word as いくない, and よかった, said on its own, is one of the most useful things in the language, meaning roughly "oh good, I'm relieved".

Nouns and な adjectives take だ, the plain counterpart of です. 学生がくせいだ, 静しずかだ. The negative is じゃない, the past だった, the negative past じゃなかった. So 学生がくせいじゃない, 学生がくせいだった, 学生がくせいじゃなかった. In careful writing the fuller ではない and ではなかった appear instead, and mean exactly the same thing.

Two warnings about だ, because it is less symmetrical than it looks. First, it is dropped far more often than です is. In casual speech 学生がくせい? with a rising tone is an ordinary question, and きれい said on its own is a complete exclamation, where きれいだ sounds oddly emphatic rather than more complete. Second, when a noun or な adjective sits inside a sentence rather than ending it, だ is often replaced by な or by である depending on what follows. You will meet this from the next lesson onwards: 学生がくせいなので, but 学生がくせいだと思おもう. The verb forms have no such complication, which is the main reason this lesson leads with them.

The four plain forms, drilled

Here is the shape of the whole system in one place, one verb from each group and the same four slots.

The drill that pays is a column at a time, out loud, against a clock. Write twenty verbs you know in their ます forms, produce all four plain forms of each without looking anything up, and check. A learner who can do that list in three minutes has bought the next fourteen lessons at a discount, because every one of them attaches something to the top row or the bottom two of this table.

Example. Rewrite 昨日きのう友ともだちに会あいましたが、映画えいがは見みませんでした in the plain form throughout.

Two verbs, both polite, both at the end of a clause. 会あいました is the polite past of 会あう, a group 1 う verb, so its て form is 会あって and its plain past is 会あった. 見みませんでした is the polite negative past of 見みる, group 2, giving 見みなかった. The result is 昨日きのう友ともだちに会あったが、映画えいがは見みなかった. Nothing else in the sentence changes: the particles, the word order and the が joining the clauses are all untouched, because politeness lives only on the verb.

Now you. Rewrite 今日きょうは寒さむかったですから、どこにも行いきませんでした in the plain form throughout.

Where the plain form is the whole sentence

One point of register before moving on, so that you do not use this lesson to be accidentally rude. When a plain form lands at the end of a spoken sentence, it marks the speech as casual, and casual in Japanese means specifically that you are speaking to a friend, a family member, someone clearly junior to you, or yourself. Used to a shopkeeper, a colleague you do not know well, or anyone older, it reads as either intimacy you have not earned or carelessness.

Written Japanese is different, and the difference is not politeness but genre. A newspaper article, a novel, a scientific paper and a Wikipedia entry are all written in plain form, and no reader takes offence, because there is no listener present to be polite to. Letters, emails and anything addressed to a named person go back to ます. This is why the same sentence, 雨あめが降ふった, is completely neutral in a weather report and pointedly casual said to your boss.

For the rest of this course the examples end in whichever form makes the pattern clearest, and you should assume you may switch the final verb to ます at will. The last lesson comes back to casual speech properly, with its contractions and its sentence-final particles, once there is enough grammar to be casual about.

Vocabulary

Everything from here builds on the top row of that four-way table. The next lesson takes a plain clause and puts a noun immediately after it, which is how Japanese says "the book I bought" without any word corresponding to "which" or "that", and it is the largest single structural gap between a beginner and someone who can read.