LearnJapanese Tae Kim's Guide to Learning Japanese

Polite Form and Verb Stems

Posted by Tae Kim

Not being rude in Japan


  1. 丁寧語 【てい・ねい・ご】 - polite language
  2. 尊敬語 【そん・けい・ご】 - honorific language
  3. 謙譲語 【けん・じょう・ご】 - humble language
  4. はい - yes (polite)
  5. いいえ - no (polite)

The Japanese we have learned so far is all well and good if you're 5-years old. Unfortunately, adults are expected to use a politer version of the language (called 丁寧語) when addressing certain people. People you will probably use 丁寧語 with are: 1) people of higher social rank, and 2) people you are not familiar with. Deciding when to use which language is pretty much a matter of "feel". However, it is a good idea to stick with one form for each person.

Later (probably much later), we will learn an even politer version of the language called honorific (尊敬語) and humble (謙譲語) form. It will be more useful than you may think because store clerks, receptionists, and such will speak to you in those forms. But for now, let's concentrate on just 丁寧語, which is the base for 尊敬語 and 謙譲語.

Fortunately, it is not difficult to change casual speech to polite speech. There may be some slight changes to the vocabulary (for example, "yes" and "no" become 「はい」 and 「いいえ」 respectively in polite speech), and very colloquial types of sentence endings are not used in polite speech. (We will learn about sentence endings in a later section.) Essentially, the only main difference between polite and casual speech comes at the very end of the sentence. You cannot even tell whether a person is speaking in polite or casual speech until the sentence is finished.

The stem of verbs


  1. 食べる 【た・べる】 (ru-verb) - to eat
  2. 泳ぐ 【およ・ぐ】 (u-verb) - to swim
  3. する (exception) - to do
  4. 来る 【く・る】 (exception) - to come
  5. 怒る 【おこ・る】 (u-verb) - to get angry
  6. 鉄拳 【てっ・けん】 - fist
  7. 休み 【やす・み】 - rest; vacation
  8. 飲む 【の・む】 (u-verb) - to drink
  9. 明日 【あした】 - tomorrow
  10. 映画 【えい・が】 - movie
  11. 見る 【み・る】 (ru-verb) - to see
  12. 行く 【い・く】 (u-verb) - to go
  13. 友達 【とも・だち】 - friend
  14. 遊ぶ 【あそ・ぶ】 (u-verb) - to play
  15. 楽しむ 【たの・しむ】 (u-verb) - to enjoy
  16. 出す 【だ・す】 (u-verb) - to bring out
  17. 走る 【はし・る】 (u-verb) - to run
  18. 走り出す 【はし・り・だ・す】 (u-verb) - to break into a run
  19. 着る 【き・る】 (ru-verb) - to wear
  20. 替える 【か・える】 (ru-verb) - to switch
  21. 着替える 【き・が・える】 (ru-verb) - to change (clothes)
  22. 付ける 【つ・ける】 (ru-verb) - to attach
  23. 加える 【くわ・える】 (ru-verb) - to add
  24. 付け加える 【つ・け・くわ・える】 (ru-verb) - to add one thing to another
  25. 言う 【い・う】 (u-verb) - to say
  26. 言い出す 【い・い・だ・す】 (u-verb) - to start talking

In order to conjugate all u-verbs and ru-verbs into their respective polite forms, we will first learn about the stem of verbs. This is often called the masu-stem in Japanese textbooks but we will call it just the stem because it is used in many more conjugations than just its masu-form. The stem is really great because it's very easy to produce and is useful in many different types of grammar.

Rules for extracting the stem of verbs
  • For ru-verbs: Remove the 「る」
    Example: 食べ食べ
  • For u-verbs: The last vowel sound changes from an / u / vowel sound to an / i / vowel sound.
  • Exceptions:
    1. する」 becomes 「し」
    2. くる」 becomes 「き」

The stem when used by itself can be a very specialized and limited way of creating nouns from verbs. While the 「の」 particle allows you to talk about verbs as if they were nouns, the stem actually turns verbs into nouns. In fact, in very rare cases, the stem is used more often than the verb itself. For example, the stem of 「怒る」(いかる) is used more often than the verb itself. The movie, "Fists of Fury" is translated as 「怒り鉄拳」 and not 「怒る鉄拳」. In fact, 「怒る」 will most likely be read as 「おこる」, a completely different verb with the same meaning and kanji! There are a number of specific nouns (such as 「休み」) that are really verb stems that are used like regular nouns. However, in general we cannot take any verb and make it into a noun. For example, the following sentence is wrong.

  • 飲みをする
    (This sentence makes sense but no one talks like this)

However, a useful grammar that works in general for stems of all verbs is using the stem as a target with a motion verb (almost always 「行く」 and 「来る」 in this case). This grammar means, "to go or to come to do [some verb]". Here's an example.

  1. 明日映画行く。- Tomorrow, go to see movie.

に」 is the stem of 「見る」 (which is 見) combined with the target particle 「に」.

The motion target particle 「へ」 sounds like you're literally going or coming to something while the 「に」 particle implies that you are going or coming for the purpose of doing something.

  1. 昨日友達遊びきた
    Yesterday, friend came to a playing activity. (Sounds a bit strange)
  2. 昨日友達遊びきた
    Yesterday, friend came to play.

The expression 「楽しみする」 meaning "to look forward to" is formed from grammar similar to this but is a special case and should be considered a set expression.

Other verbs are also sometimes attached to the stem to create new verbs. For example, when 「出す」 is attached to the stem of 「走る」, which is 「走り」, you get 「走り出す」 meaning "to break out into a run". Other examples include 「切り替える」, which means "to switch over to something else", and 「付け加える」, which means "to add something by attaching it". You can see how the separate meanings of the two verbs are combined to create the new combined verb. For example, 「言い出す」 means "to start talking", combining the meaning, "to speak" and "to bring out". There are no general rules here, you need to just memorize these combined verbs as separate verbs in their own right.

Things that are written in a formal context such as newspaper articles also use the stem as a conjunctive verb. We will come back to this later in the formal expression lesson.

Using 「~ます」 to make verbs polite


  1. 明日 【あした】 - tomorrow
  2. 大学 【だい・がく】 - college
  3. 行く 【い・く】 (u-verb) - to go
  4. 先週 【せん・しゅう】 - last week
  5. 会う 【あ・う】 (u-verb) - to meet
  6. 晩ご飯 【ばん・ご・はん】 - dinner
  7. 食べる 【た・べる】 (ru-verb) - to eat
  8. 面白い 【おも・しろ・い】(i-adj) - interesting
  9. 映画 【えい・が】 - movie
  10. 見る 【み・る】 (ru-verb) - to see

Of course, the reason I introduced the verb stem is to learn how to conjugate verbs into their polite form... the masu-form! The masu-form must always come at the end of a complete sentence and never inside a modifying relative clause. When we learn compound sentences, we will see that each sub-sentence of the compound sentence can end in masu-form as well.

To conjugate verbs into the masu-form, you attach different conjugations of 「ます」 to the stem depending on the tense. Here is a chart.

A conjugation chart with sample stem 「遊び
ます conjugations Stem+ます
Plain ます 遊びます
Negative ません 遊びません
Past ました 遊びました
Past-Neg ませんでした 遊びませんでした


  1. 明日大学行きます
    Tomorrow, go to college.
  2. 先週、ボブに会いましたよ。
    You know, met Bob last week.
  3. 晩ご飯食べませんでしたね。
    Didn't eat dinner, huh?
  4. 面白くない映画見ません
    About not interesting movies, do not see (them).

Using 「です」 for everything else


  1. かわいい (i-adj) - cute
  2. 静か 【しず・か】 (na-adj) - quiet
  3. 子犬 【こ・いぬ】 - puppy
  4. とても - very
  5. 好き 【す・き】 (na-adj) - likable; desirable
  6. 昨日【きのう】 - yesterday
  7. 時間 【じ・かん】 - time
  8. ある (u-verb) - to exist (inanimate)
  9. その - that (abbr of 「それの」)
  10. 部屋 【へ・や】 - room
  11. 先週 【せん・しゅう】 - last week
  12. 見る 【み・る】 (ru-verb) - to see
  13. 映画 【えい・が】 - movie
  14. 面白い 【おも・しろ・い】(i-adj) - interesting

For any sentence that does not end in a ru-verb or u-verb, the only thing that needs to be done is to add 「です」 or 「でした」. You can also do this for substituted nouns (both 「の」 and 「ん」) by just treating them like regular nouns. Another important thing to remember is that if there is a declarative 「だ」, it must be removed. In being polite, I guess you can't be so bold as to forwardly declare things the way 「だ」 does. Just like the masu-form, this must also go at the end of a complete sentence. Here is a chart illustrating the conjugations.

i-adjective (だ cannot be used)
Casual Polite
Plain かわいい かわいいです
Negative かわいくない かわいくないです
Past かわいかった かわいかったです
Past-Neg かわいくなかった かわいくなかったです
na-adjective/noun (might have to remove だ)
Casual Polite
Plain 静か(だ) 静かです
Negative 静かじゃない 静かじゃないです
Past 静かだった ※静かでした
Past-Neg 静かじゃなかった 静かじゃなかったです

※ Notice in the case of noun/na-adjective only, the past tense becomes 「でした」. A very common mistake is to do the same for i-adjectives. Remember 「かわいいでした」 is wrong!


  1. 子犬とても好きです
    About puppies, like very much. (The most natural translation is that someone likes puppies very much but there is not enough context to rule out that the puppies like something very much.)
  2. 昨日時間なかったんです
    It was that there was no time yesterday.
  3. その部屋あまり静かじゃないです
    That room is not very quiet.
  4. 先週見た映画は、とても面白かったです
    Movie saw last week was very interesting.

※ Reality Check

I have heard on a number of occasions that the negative non-past conjugation as given here is not an "officially" correct conjugation. Instead what's considered to be a more "correct" conjugation is to actually replace the 「ないです」 part with 「ありません」. The reasoning is that the polite negative form of the verb 「ある」 is not 「ないです」 but 「ありません」. Therefore, 「かわいくない」 actually becomes 「かわいくありません」 and 「静かじゃない」 becomes 「静かじゃありません」.

The reality of today's Japanese is that what's supposed to be the "official" conjugation sounds rather stiff and formal. In normal everyday conversations, the conjugation presented here will be used almost every time. While you should use the more formal conjugations for written works using the polite form, you'll rarely hear it in actual speech. In conclusion, I recommend studying and becoming familiar with both types of conjugations.

A more formal negative conjugation
Casual Polite
Negative かわいくない かわいくありません
Past-Neg かわいくなかった かわいくありませんでした
Negative 静かじゃない 静かじゃありません
Past-Neg 静かじゃなかった 静かじゃありませんでした


  1. その部屋あまり静かじゃないですよ。
    You know, that room is not very quiet.
  2. その部屋あまり静かじゃありませんよ。
    You know, that room is not very quiet.

「です」 is NOT the same as 「だ」


  1. そう - so
  2. 思う 【おも・う】 (u-verb) - to think
  3. はい - yes (polite)
  4. 答える 【こた・える】 (ru-verb) - to answer

Many of you who have taken Japanese classes have probably been taught that 「です」 is the polite version of 「だ」. However, I want to point some several key differences here and the reasons why they are in fact completely different things. It is impossible to fully explain the reasons why they are fundamentally different without discussing grammar that have yet to be covered so I would like to target this toward those who have already started learning Japanese and have been incorrectly misinformed that 「だ」 is the casual version of 「です」. For the rest of you new to this, you can easily skip this part.

I'm sure most of you have learned the expression 「そう」 by now. Now, there are four ways to make a complete sentence using the state-of-being with 「そう」 to produce a sentence that says, "That is so."

Different ways to say, "That is so."

  1. そう
  2. そうだ。
  3. そうです。
  4. そうでございます。

The first 「そう」 is the implied state-of-being and 「そうだ」 is the declarative. As I've stated before, the non-assuming soft spoken 「そう」 is often used by females while the more confident 「そうだ」 is often used by males.

そうです」 is the polite version of 「そう」, created by attaching 「です」 to the noun. 「そうです」 is not the polite version of 「そうだ」 where the 「だ」 is replaced by 「です」 and I'll explain why.

Perhaps we wanted to make that sentence into a question instead to ask, "Is that so?" There are several ways to do this but some possibilities are given in the following. (This grammar is covered in a later section.)

Different ways to ask, "Is that so?"

  1. そう
  2. そうか?
  3. そうですか?

As I've explained before, the 「だ」 is used to declare what one believes to be a fact. Therefore, 「そうだか?」 is not a valid way to ask a question because it is declaring a fact and asking a question at the same time. But the fact that 「そうですか」 is a valid question shows that 「です」 and 「だ」 are essentially different. 「そうです」, in showing respect and humbleness, is not as assertive and is merely the polite version of 「そう」.

Besides the difference in nuance between 「だ」 and 「です」, another key difference is that 「だ」 is used in many different types of grammar to delineate a relative clause. 「です」, on the other hand, is only used at the end of a sentence to designate a polite state-of-being. For instance, consider the two following sentences. (This grammar is covered in a later section.)

  • そう思います
    I think that is so.
  • そうです思います
    (Incorrect sentence)

そう思います」 is valid while 「そうです思います」 is not because 「です」 can only go at the end of the sentence. 「です」 can only be in a relative clause when it is a direct quote of what someone said such as the following.

  • 「はい、そうです」と答えた

In conclusion, replacing 「です」 with 「だ」, thinking one is the polite equivalent of the other or vice-versa will potentially result in grammatically incorrect sentences. It is best to think of them as totally separate things (because they are).