Japanese Verbs plus Polite and Plain Styles

Japanese can be divided into 2 types of speech - Polite and Plain styles (or forms).
What you have learned so far until this lesson are all in polite style.
That's to say, those sentences which ended with です (desu), でした (deshita), ではありません (dewa arimasen), ではありませんでした (dewa arimasen deshita), ます (masu), ました (mashita), ません (masen), ませんでした are all polite style.
On the other hand, Plain style, which is shorter when compared to Polite style are sentences ended with だ (da), だった (datta), ない (nai), た (ta), なかった (nakatta), etc.
You can use Polite style anytime, talking to anybody. When talking to someone who you have met for the first time or not close enough, or to your superiors, it's best to speak in Polite style in order to be polite. It's considered rude if you speak in Plain style to these people.
Whereas for Plain style, you use it when you are talking to family members, colleagues or close friends. It will seem strange to speak in polite style to them. Besides, Plain style is commonly used in written work like Newspaper, books, etc. However most letters are written in the Polite style.

How to Decide If The Sentence is Polite or Plain Style?

The style of the speech is decided by the last Japanese verb (for verb sentence) that you used in a sentence. Even if you have used many plain forms within the sentence, as long as it ends with polite form, the sentence is considered to be Polite style or form.
On the contrary, even if you have put in many polite forms within the sentence, as long as it ends with plain form, the sentence becomes Plain style. For example consider the 2 following sentences...

1. わたしはあしたがっこうへ いく と おもいます。
   watashi wa ashita gakkou e iku to omoimasu
2. わたしはあしたがっこうへ いく と おもう。
   watashi wa ashita gakkou e iku to omou

Both sentences mean "I think I am going to school tomorrow". The underlined Japanese verb いく is the dictionary-form of いきます (ikimasu) which means "to go". Dictionary-form is considered one of the plain form (I will go into that later).
As you can see, the first sentence ended with the Japanese verb おもいます (omoimasu) which means "to think". This is a polite ます-form (masu-form) verb. Therefore this sentence is considered to be a Polite style sentence.
However, the second sentence ended with the dictionary-form (plain form) of "to think", おもう (omou). In this case, this sentence is considered to be a Plain style sentence.

Plain Style of Japanese Verbs

Actually the Polite style that you have learned so far is not the basic of Japanese. The basic of Japanese is in the Plain style. The dictionary-form that I mentioned just now is one of the Plain style. The reason why it is called dictionary-form is because it is the form you can find in dictionary.
Dictionary-form is also considered to be the Present Affirmative of Plain style. And you will get to learn the other forms in Plain style in future lessons. See the following table for the various forms in Plain style for Japanese verbs.

	Polite Style	Plain Style
Present Affirmative	ます	じしょ-form or dictionary-form
Present Negative	ません	ない-form or nai-form
Past Affirmative	ました	た-form or ta-form
Past Negative	ませんでした	なかった-form or nakatta-form

The 3 Groups of Japanese Verbs in Dictionary-Form

Japanese verbs can be divided into 3 groups.
Group 1 verbs are verbs ended with う (u), く (ku), ぐ (gu), す (su), つ (tsu), ぬ (nu), ぶ (bu), む (mu), and the words of あ (a) column, う (u) column, お (o) column in the hiragana chart plus る (ru). For example, the following are group 1 verbs:

• いう (iu) - say, tell
• いく (iku) - go
• およぐ (oyogu) - swim
• なおす (naosu) - fix, repair
• まつ (matsu) - wait
• しぬ (shinu) - die
• あそぶ (asobu) - play
• のむ (nomu) - drink
• わかる (wakaru) - understand
• ねむる (nemuru) - sleep
• まもる (mamoru) - protect

There are some exceptions whereas the verbs don't fulfil the above rules but still considered as group 1 verbs. Or you can say that they look like group 2 verbs but are actually group 1 verbs. For example like はいる (hairu), はしる (hashiru) and かえる (kaeru). There are many other exceptions but for the meantime I will only list three of them.
Group 2 verbs are verbs ended with い (i) column, え (e) column in the hiragana chart plus る (ru). The following are some examples of group 2 verbs:

• たべる (taberu) - eat
• おきる (okiru) - get up, rise

Group 3 verbs are くる (kuru) and all verbs ended with する (suru). The following are some examples of group 3 verbs:

• くる (kuru) - come
• べんきょうする (benkyou suru) - study
• さんぽする (sanpo suru) - stroll, walk

In next lesson, you will get to learn how to change the verbs from dictionary-form to masu-form and nai-form for all the three groups.