From Conjugated Form to Dictionary Form: 食べました, 読んだ, 来られる
Hiroki Obara · Developer
Japanese dictionaries, including JMdict, the free dictionary many learners use, list verbs in their dictionary form: 食べる (to eat), 読む (to read), 来る (to come). In a real book, though, you rarely meet a verb in that form. You meet 食べました, 読んだ, 来られる.
This is where many learners get stuck. You want to look a word up because you don’t know it, and you can’t look it up because you don’t know the form the dictionary uses. This post covers the steps for getting from a conjugated form back to the dictionary form, and the forms that are hardest to undo. In the second half I describe exactly which forms the automatic lookup in Niho, the reading app I make, can undo and which it can’t.
The basic steps
A conjugated form is usually a stem with endings stacked on it. To get back, you take the endings off one at a time.
1. Remove ます or です and their forms. 食べました loses ました and leaves 食べ. 読みます leaves 読み.
2. Remove ない, た, て, れる・られる, させる and so on. If several are stacked, work from the end.
3. Build the dictionary form from what is left. This is where the verb group matters.
- Ichidan verbs (the 食べる and 見る type): add る. 食べ → 食べる, 見 → 見る.
- Godan verbs (the 読む and 書く type): change the final i-row sound to the matching u-row sound. 読み → 読む, 書き → 書く.
- Irregular verbs: just two, 来る and する. Learn their forms as they are.
Grammar books use more detailed names, but for looking words up, these three groups are enough.
Forms that are hard to undo
Even when the rules work, some forms trip learners up again and again. Here are six of them.
んだ and んで. 読んだ, 飛んだ and 死んだ all end in んだ, but their dictionary forms are 読む, 飛ぶ and 死ぬ. The shape alone doesn’t tell you whether to go back to む, ぶ or ぬ.
った and って. 買った, 待った and 帰った come from 買う, 待つ and 帰る. Three possibilities again. 帰る ends in る but is a godan verb, so if you treat it as ichidan you will get its other forms wrong. And 行った is the past of 行く (iku, to go), but the same characters are also the past of 行う (okonau, to carry out). Only the reading differs.
来 with a changing reading. 来る (kuru), 来ない (konai), 来た (kita) and 来られる (korareru) all use the same character with different readings. Written in kanji, the dictionary form is easy to guess. Written in kana as こない, it is much harder to get back to 来る.
Long stacks. 食べさせられなかった is 食べる plus させる (causative), られる (passive), ない (negative) and た (past). Take them off one by one and you get there, but until you are used to it, you can’t see where to cut.
Potential verbs and ら-dropping. 読める is the potential form of 読む, but dictionaries often list 読める as a separate entry. 見れる is the spoken form of 見られる with the ら dropped, and some dictionaries list it too.
Special honorific verbs. いらっしゃる, おっしゃる, くださる, なさる and ござる take い, not り, before ます. You say いらっしゃいます, not いらっしゃります. Apply the usual rule, changing い to う, and you get いらっしゃう, which is not a word.
〜られる has more than one meaning
来られる is tricky for another reason too. 〜れる・られる can be passive (先生にほめられる, to be praised by the teacher), potential (朝早く起きられる, to be able to get up early), honorific (先生が来られる, the teacher comes) or spontaneous (昔のことが思い出される, the past comes back to mind). You can always get back to the dictionary form, but which meaning it has is something only the context decides.
When 〜られる turns up in dialogue in a novel, keep the honorific reading in mind. How to tell keigo apart is in Reading Keigo in Japanese Novels.
What Niho’s lookup can undo
Niho, an app I make for iPhone and iPad, lets you read Aozora Bunko books with a built-in dictionary. It is free, with no ads and no in-app purchases.
Long-press to select text and tap Look up, and a conjugated form is turned back into its dictionary form before it is looked up. Under the headword, one line shows how it got there, for example 食べました → 食べる · polite past, stem. The common labels are these.
| Label | Meaning |
|---|---|
| polite / polite past | ます / ました |
| polite negative | ません |
| stem | undone from the form before ます |
| past / te-form | た / て |
| negative / negative past | ない / なかった |
| passive / passive or potential | passive / passive or potential |
| potential | potential |
| causative | させる |
| progressive | ている |
| volitional | よう / おう |
| conditional (-ba) / (-tara) | ば / たら |
These are the forms Niho can undo:
- ます forms: ます, ました, ません, ませんでした, ましょう, まして
- ない forms: ない, なかった, なくて, なければ, ないで, ず, ずに, ぬ
- て and た forms: て, た, たら, たり, including the special 行った → 行く
- ば forms, volitional forms (読もう, 食べよう) and imperative forms (読め, 食べろ, しろ, 来い)
- Passive, potential and causative: 読まれる, 読める, 読ませる, 食べられる, 来られる, される, できる
- Helpers after て: ている, ていた, ています, てある, ておく, てしまう, ちゃう, てみる, ていく, てくる, てくれる, てもらう, てあげる, てほしい
- Endings after the ます stem: たい, たがる, ながら, そう, すぎる, やすい, にくい, 方 (kata, way of), なさい
- い-adjectives: 高かった, 高くない, 高くなかった, 高くて, 高ければ, 高く, 高さ
Stacks of these work too. Look up 食べさせられなかった and you get 食べる, with the line listing negative past, negative, passive or potential, causative, in the order they were removed. The forms of 来る such as 来ない, 来た and 来られる work, and so do する verbs like 勉強した. A する verb goes back to the noun, 勉強, rather than to 勉強する.
Forms written in kana work as well. たべました also gets you to 食べる.
What it can’t undo, and what to do then
Some forms do not work.
The ます forms of the five honorific verbs. いらっしゃいます, おっしゃいます, くださいました, なさいました, ございました and other forms built on the い before ます do not go back to the dictionary form.
What you see instead depends on the word. いらっしゃいます shows the interjection いらっしゃい (“welcome”; its first sense is the honorific “come, go, stay”). くださいました shows ください and なさいました shows なさい. With those three you can still guess the meaning. The real problem is おっしゃいます and おっしゃいました, which bring up an unrelated short word.
The other forms of the same verbs do work. いらっしゃった, おっしゃった, くださった and なさった go back to いらっしゃる, おっしゃる, くださる and なさる. ございます and なさいます are listed in the dictionary as they are, so they come up directly.
When you meet one of these, one fix is to remember the い rule above and undo it in your head: いらっしゃい → いらっしゃる. There are only five, so they are worth learning by heart. You can also tap Jisho in the selection menu to search the web dictionary.
でした and だった after na-adjectives and nouns. For きれいでした or 静かな, Niho doesn’t undo anything. It looks for the longest word in the dictionary from the start of your selection, and finds きれい or 静か. You get the word, but no explanation line.
Old kana spelling. Conjugations in the old spelling, such as 言ふ or 思はれる, are not covered. How to read them is in Reading Old Kana Spelling.
Sometimes the form is undone correctly but the first word shown is not the one you wanted.
- 来た shows the interjection 来た (as in よし、来た, “right, here we go”) first, with 来る below it.
- 行った shows both 行う and 行く. 行う is the one on top.
- Select only した or いた and nouns with the same reading, such as 舌 (tongue) or 板 (board), come first.
All of these happen because a word with exactly that form is in the dictionary, or because the same characters belong to another verb. Look at the other words listed on the sheet and choose the one that fits the sentence. For a short form like した, select from the word before it, as in 勉強した, and you will get the word you want.
Even when the line says “passive or potential,” the られる may be honorific, as described above. The line is a record of the endings removed, not a decision about meaning.
Learning the rules, and getting used to them by reading
There is a view that you don’t need to learn all the conjugation rules before you start reading. Even so, three things are worth looking at in a table early on: where んだ and った come from, the forms of 来る and する, and the five honorific verbs. They are few, and they come up all the time.
The rest can stick better when you get used to it as you read. If you read the line showing how each lookup was undone, before long you start doing the same undoing in your head before you tap. Forms you met many times in a book last longer than rules learned from a table. How to use that line is also in Practical Tips for Reading Japanese with Niho.
Looking up conjugated forms in Niho
You don’t need to make an exact selection in Niho. Long-press from the start of the word and select a little more than you need. Niho looks for the longest word in the dictionary from the start of the selection and lists shorter candidates after it. For a conjugated verb, it is fine to include the particle that follows. How to find where words begin is in Reading Japanese Without Spaces.
The JMdict and KANJIDIC2 dictionaries are built into the app and work offline. Words you look up are saved to your word book with the sentence you met them in. In the quiz’s Fill in the blank questions, the real sentence from the book is shown with the whole conjugated form blanked out, so you practise recalling a word you learned in dictionary form in the shape it took in the book.
Getting Started with Niho walks through your first book.
