Plain form and polite form: When to use which in Japanese?

In Japanese, you can put sentences in a plain form or a polite form.

• The plain form is used in informal conversations, with close friends, family, children, and people of lower rank at work or school. This is also the form you use in all subordinate clauses, regardless of the social situation.

• The polite form is used in formal situations like when you're speaking to a stranger, an elder, or to a social superior at work or school.

In this post, we’ll explore how and when to use each of these forms and cover the cultural nuances of how to choose between formal and informal speech in any situation. Let’s give it a try!

In Japanese, when a verb, adjective, or noun comes at the end of a sentence (acting as the predicate), its ending will reflect how polite the speaker wants to be. The two most common forms are the plain form and the polite form.

While the plain/polite distinction exists in all tenses, the polite form will usually end with some form of ます (transcribed masu) or です (transcribed desu). Compare the non-past plain and polite forms below:

In this article, we'll focus on how and when you should use each of these forms. To learn more about the plain and polite endings and how to form the plain and polite forms of nouns, verbs, and adjectives, we suggest you start with these three posts:

1. Forming the plain and polite forms of Japanese verbs

2. How to use adjectives in Japanese

3. How to form Japanese sentences with a noun as the predicate

For now, though, let's focus back in on when to use each form!

As a general rule, using polite form is always a safe choice, but there are some situations where it is expected and required. Here’s an incomplete list.

• any kind of public speaking, including speaking before the class at school

• writing a formal letter or email

• speaking to adults and teenagers you don’t know, and anyone older than you

• speaking to teachers, professors, doctors, and others in highly respected professions

• speaking to anyone who has been at your school/workplace longer than you have

• addressing salespeople, train station employees, etc.

• speaking to early non-native learners of Japanese (who may have not yet learned plain form).

It’s usually safe to use the plain form in any casual situation, so long as you’re speaking or texting with someone from one of the following groups:

• your own family, regardless of their age

• any young child outside of school

• friends your same age (same year in school) or younger

• coworkers who are newer to your workplace than you are (though you can use polite form here too)

Remember, though that regardless of the level of formality you should always use the plain form in a subordinate clause! The sentences below are polite (you can tell from the ending of the sentence), but the subordinate clauses still use the plain form:

One way to remember to use the plain form in subordinate clauses, is to keep in mind the common expressions follow subordinate clauses, as these will almost always follow a plain form. Here are a few expressions to start with:

• 〜から (transcribed kara, meaning “because”)

• 〜と言っていました (transcribed to itte imashita, meaning “someone was saying that...”)

• 〜そうです (transcribed sō desu, meaning “I heard that...”)

• 〜と言われます (transcribed to iwaremasu, meaning “It is said that...”)

• 〜し (transcribed shi, meaning “because... (and other reasons)”)

• 〜といい (transcribed to ii, meaning “I hope that...”)

• 〜と... (transcribed to, meaning “If...”)

• 〜と考えられています (transcribed to kangaerarete imasu, meaning “it is thought that…”)

• 〜と思われています (transcribed to omowarete imasu, meaning “it is believed that…”)

But there are lots more Japanese expressions that commonly follow subordinate clauses (and the plain form)! Keep a sharp eye out for them as you read other articles in this series!

There are a couple of the common mistakes I hear Japanese learners make when they're trying to choose between the plain and polite forms. Let's go over these mistakes, and I'll give you some tips on how you can avoid them!

• Misuse of だ

  The important thing to remember about だ (transcribed da) is that it is only used after nouns and na-adjectives. If you have a verb or an i-adjective with a だ (transcribed da) on it, you have a problem!

  i-adjective

  ✅ ギターができる人がかっこいいと思う。

  Transcription: Gitā ga dekiru hito ga kakkoii to omou.

  Translation: I think that people who can play the guitar are cool.

  ❌ ギターができる人がかっこいいだと思う。

  Transcription: Gitā ga dekiru hito ga kakkoii da to omou.

  Here, だ (transcribed da) is incorrect because かっこいい (transcribed kakkoii, meaning “cool”) is an i-adjective.

  However, you also have to careful not to leave だ (transcribed da) out when it’s necessary. Let’s look at some examples.

  noun

  ✅ サークルの会長だから、週に3回練習会に行きます。

  Transcription: Sākuru no kaichō da kara, shū ni san kai renshūkai ni ikimasu.

  Translation: I go to rehearsals three times a week because I am the club president.

  ❌ サークルの会長から、週に3回練習会に行きます。

  Transcription: Sākuru no kaichō kara, shū ni san kai renshūkai ni ikimasu.

  This time, だ (transcribed da) is required because 会長 (transcribed kaichō, meaning “president”) is a noun.

• Overuse of です [desu] and ます [masu]

  To avoid overusing です (transcribed desu) and ます (transcribed masu), remember that in general, you should only have one polite ending per sentence, and the polite ending should come at the end of the sentence. It may be です (transcribed desu) or ます (transcribed masu), not both.

  While occasionally the polite ending will not be the very last thing in a sentence (as when a sentence ends with a sentence-ending particle!) it should be close to the end in a neutral situation, and you certainly shouldn't have a lot of polite endings within a single sentence.

The answer to this question is both yes and no. If you're a non-native learner of Japanese, people you speak to will be forgiving of your mistakes. So long as you’re trying your best to be courteous, it’s unlikely that you will ever offend someone by choosing the wrong grammar form. You can relax!

That being said, speaking exclusively in polite form with someone who considers you a friend might make that person feel as if you’re “holding them at arm’s length.” Additionally, native speakers of Japanese acquire plain form first as children, so if you’re using polite form to a very young child and they don’t seem to understand you, try switching to plain form.

Let's review what we learned about the Japanese plain vs. polite form.

• The polite form is used in more formal situations. Usually only the last substantial word in a sentence will be in this form.

• The plain form is used in casual speech with friends, family, and children, but is also used in embedded clauses.

Always remember that sentence that includes a plain form can still be formal! Just check the form of the final word. If it ends in a form of ます (transcribed masu) or です (transcribed desu), it's polite!

Ready to practice what you've learned? Check out our plain vs. polite form activities to test your skills! Happy learning!