In the Japanese language, there are two primary levels of speech: the plain form (casual) and the polite form (formal). Knowing when and how to use these forms is important for effective communication in Japanese. The plain form, or jishokei (辞書形) in Japanese, is used in casual conversations with friends, family, or people of the same age or status. The polite form, or masukei (ます形) in Japanese, is used in formal situations, such as speaking with strangers, superiors, or in customer service.

This article will explain the plain and polite forms, using verbs and adjectives as examples.

Verbs: Plain Form vs. Polite Form

Japanese verbs are conjugated differently depending on the level of formality.

There are three groups of verbs in the Japanese language: the u-verbs, the ru-verbs, and the irregular verbs. The examples below will be using the ru-verb 食べる (taberu) – to eat.

Plain Form:

1. 毎日野菜を食べる。
   (Mainichi yasai o taberu.)
   I eat vegetables everyday.
2. あまり野菜を食べない。
   (Amari yasai o tabenai.)
   I seldom eat vegetables.
3. 毎日野菜を食べる？
   (Mainichi yasai o taberu?)
   Do you eat vegetables everyday?

Polite Form:

1. 毎日野菜を食べます。
   (Mainichi yasai o tabemasu.)
2. あまり野菜を食べません。
   (Amari yasai o tabemasen.)
3. 毎日野菜を食べますか。
   (Mainichi yasai o tabemasu ka.)

For interrogative sentences, the polite form uses the question particle かat the end of the sentence without a question mark. On the other hand, in the plain form, no question particle is needed but a question mark is included (if it’s written).

The above examples are in the present tense. Next, let’s take a look at the difference in the plain and polite forms in the past tense.

Plain Form:

1. 毎日野菜を食べた。
   (Mainichi yasai o tabeta.)
   I ate vegetables everyday.
2. あまり野菜を食べなかった。
   (Amari yasai o tabenakatta.)
   I seldom ate vegetables.
3. 毎日野菜を食べた？
   (Mainichi yasai o tabeta?)
   Did you eat vegetables everyday?

Polite Form:

1. 毎日野菜を食べました。
   (Mainichi yasai o tabemashita.)
2. あまり野菜を食べませんでした。
   (Amari yasai o tabemasen dehista.)
3. 毎日野菜を食べましたか。
   (Mainichi yasai o tabemashita ka.)

In summary, verbs in the plain and polite forms conjugate differently. The negative and the past forms are also conjugated differently. Moreover, the plain form of a question does not require a question particle, whereas the polite form does. Now that you know the differences between the two forms, you can practice speaking in plain or polite form in your Japanese classes.