Japanese verb groups: classification and conjugation

The verb is the engine of the Japanese sentence. Unlike English where conjugation changes according to person (I, you, he…), Japanese verbs remain invariable regardless of the subject. The modification occurs only according to tense and level of politeness. To construct correct sentences, you must first identify which group a verb belongs to. This identification determines everything that follows in learning Japanese grammar.

The Dictionary Form: The Starting Point

Before conjugating, you need to know the neutral form of the verb. This is called the “dictionary form” (jisho-kei) or neutral form. It’s the one you find in lexicons. An absolute rule governs this form: all Japanese verbs end with the “u” sound. Be careful, this doesn’t mean they all end with the letter “u” alone, but with a syllable containing the “u” sound (u, ku, su, tsu, nu, bu, mu, ru, gu). It’s this ending that determines the group.

Group 1: Godan Verbs (五段)

This group is the largest. They’re called “Godan” or 5-step verbs. They encompass the majority of action verbs. To recognise them, simply look at the last syllable. If the verb doesn’t end in “iru” or “eru”, it’s almost automatically a Group 1 verb. Here are the 9 possible endings for Godan verbs, with concrete examples:

Ending	Example (Kanji + Kana)	Romaji	Translation
u (う)	買う (かう)	kau	to buy
ku (く)	書く (かく)	kaku	to write
gu (ぐ)	泳ぐ (およぐ)	oyogu	to swim
su (す)	話す (はなす)	hanasu	to speak
tsu (つ)	待つ (まつ)	matsu	to wait
nu (ぬ)	死ぬ (しぬ)	shinu	to die
bu (ぶ)	遊ぶ (あそぶ)	asobu	to have fun / to play
mu (む)	飲む (のむ)	nomu	to drink
ru (る)	取る (とる)	toru	to take

Note carefully the “ru” (る) ending. It often causes problems for beginners as it also exists in Group 2. For Group 1, the rule is simple: if the vowel just before “ru” is “a”, “u” or “o”, the verb belongs to Group 1. Examples:

• Noboru (登る – to climb): before “ru”, we have the “o” sound. It’s a Godan.
• Owaru (終わる – to finish): before “ru”, we have the “a” sound. It’s a Godan.

Group 2: Ichidan Verbs (一段)

The second group, called Ichidan, is simpler to handle. These verbs always end with the syllable “ru” (る). But be careful, there’s an additional phonetic condition. To belong to this group, the sound preceding the final “ru” must be “i” or “e”. This gives endings in -iru or -eru. Common examples:

• Taberu (食べる – to eat): ends in -eru.
• Miru (見る – to see): ends in -iru.
• Neru (寝る – to sleep): ends in -eru.
• Okiru (起きる – to get up): ends in -iru.

Visually, in kanji, the difference is often clear: the “ru” (る) stands out from the kanji. In 食べる (taberu), the “be” is included in the kanji or written in hiragana, but the “ru” is always visible at the end.

Group 3: Irregular Verbs

This is the good news about Japanese: there are only two irregular verbs to learn by heart. Unlike Romance languages where exceptions abound, here the list is closed. The two verbs are:

• Suru (する): to do
• Kuru (来る): to come

The verb Suru is particularly useful. It serves to transform nouns into action verbs. You take a word from the basic vocabulary, add “suru”, and you get a verb. Examples of compound verbs with Suru:

• Benkyou (study) + suru = Benkyou suru (勉強する – to study).
• Shigoto (work) + suru = Shigoto suru (仕事する – to work).
• Denwa (telephone) + suru = Denwa suru (電話する – to telephone).

The Exception Trap: False Friends of Group 2

Some verbs look exactly like Ichidan (Group 2) because they end in “iru” or “eru”, but they actually belong to Group 1 (Godan). You must memorise them as they conjugate differently. Here are the most frequent exceptions to know from the beginning:

• Kaeru (帰る – to return home): ends in -eru, but it’s Group 1.
• Hashiru (走る – to run): ends in -iru, but it’s Group 1.
• Kiru (切る – to cut): ends in -iru, but it’s Group 1. (Note: Kiru 着る “to wear clothes” is indeed Group 2).
• Shiru (知る – to know): ends in -iru, but it’s Group 1.
• Hairu (入る – to enter): ends in -iru, but it’s Group 1.

Mnemonic tip: For “Kaeru” (to return), imagine returning home with your 5 senses (5 = Godan).

Polite Conjugation: The -Masu Form

Once the group is identified, we move to conjugation. The most useful form for starting to speak is the polite form, called the “-Masu form”. It’s the one used with strangers, teachers or colleagues. It’s standard and versatile. The transformation mechanism changes according to the group.

Group 1 (Godan) Conjugation

The rule is phonetic: change the final “u” sound to “i” sound, then add “masu”. This is why this group is called “Godan” (5 rows), because the verb navigates across the vowel columns (a, i, u, e, o). Here, we move from the U column to the I column. Godan transformation table:

Verb (Dictionary)	Transformation (u -> i)	Masu Form (Polite)	Translation
Kau (かう)	Kai	Kaimasu (かいます)	I buy / He buys
Kaku (かく)	Kaki	Kakimasu (かきます)	I write
Oyogu (およぐ)	Oyogi	Oyogimasu (およぎます)	I swim
Hanasu (はなす)	Hanasi (Hanashi)	Hanashimasu (はなします)	I speak
Matsu (まつ)	Machi	Machimasu (まちます)	I wait
Shinu (しぬ)	Shini	Shinimasu (しにます)	He dies
Asobu (あそぶ)	Asobi	Asobimasu (あそびます)	I play
Nomu (のむ)	Nomi	Nomimasu (のみます)	I drink
Toru (とる)	Tori	Torimasu (とります)	I take

Notice the slight spelling modifications to preserve correct pronunciation:

• Su becomes Shi (Hanasu -> Hanashimasu).
• Tsu becomes Chi (Matsu -> Machimasu).

Group 2 (Ichidan) Conjugation

This is the simplest conjugation. The method consists of simply removing the final “ru” syllable and replacing it with “masu”. The verb stem doesn’t change.

• Taberu (to eat) -> Remove “ru” -> Tabe -> Tabemasu (食べます).
• Miru (to see) -> Remove “ru” -> Mi -> Mimasu (見ます).
• Okiru (to get up) -> Remove “ru” -> Oki -> Okimasu (起きます).

It’s a mechanical operation: cut and paste.

Group 3 (Irregular) Conjugation

As there are only two verbs, you must learn their transformation by heart. The stem changes pronunciation completely.

• Suru (to do) becomes Shimasu (します).
  • Benkyou suru -> Benkyou shimasu (I study).
• Kuru (to come) becomes Kimasu (来ます).
  • Pay attention to the kanji pronunciation: in 来る it reads “Ku”, in 来ます it reads “Ki”.

The Polite Negative Form (Masen)

Once you understand the “Masu” mechanism, negation becomes child’s play. Simply replace “masu” with “masen”. The stem construction remains exactly the same for all three groups. Concrete examples:

• Group 1: Iku (to go) -> Ikimasu (I go) -> Ikimasen (I don’t go).
• Group 2: Taberu (to eat) -> Tabemasu (I eat) -> Tabemasen (I don’t eat).
• Group 3: Suru (to do) -> Shimasu (I do) -> Shimasen (I don’t do).

This regularity greatly facilitates oral expression. Once you master the transformation to the “masu” stem, you gain access to the present, future (which is the same tense in Japanese) and negation.

Practical Case: Analysing a New Verb

Let’s take an unknown verb for practice: Kiku (聞く – to listen).

• Observation: It ends in “u” (more precisely “ku”).
• Test: Does it end in “iru” or “eru”? No.
• Conclusion: It’s a Group 1 (Godan) verb.
• Conjugation:
  • Change the final “u” to “i”: Kiku -> Kiki.
  • Add masu: Kikimasu (I listen).

Let’s take another verb: Oshieru (教える – to teach).

• Observation: It ends in “ru”.
• Test: The sound before “ru” is “e” (Oshie-ru).
• Conclusion: It’s a Group 2 (Ichidan) verb.
• Conjugation:
  • Remove “ru”: Oshieru -> Oshie.
  • Add masu: Oshiemasu (I teach).

This mental gymnastics becomes automatic with a bit of practice. The classic mistake consists of treating an Ichidan verb like a Godan (saying “Oshierimasu” instead of “Oshiemasu”). To avoid this, always check the vowel that precedes the “ru”. Mastering these three groups is the foundation of the language. All other verb forms (-Te form for requests, -Ta form for past tense, potential form, etc.) are based on this initial classification. An error in grouping at the start leads to a chain of conjugation errors. Take time to properly classify each new verb learned in your vocabulary.