Ichidan Verbs

Definition:

Ichidan verbs (一段動詞, ichidan-dōshi, literally “one-step/column verbs”) are the second major class of Japanese verbs. Unlike godan verbs, which shift across five vowel rows during conjugation, ichidan verbs use only a single row — they never change their stem vowel. This makes their conjugation beautifully regular and predictable. They are also called Group 2 verbs, RU-verbs, or Type 2 verbs.

Identifying Ichidan Verbs

Ichidan verbs always end in -iru (〜いる) or -eru (〜える) in their dictionary form. The conjugation rule is simple:

> Remove the final -ru and add the appropriate suffix.

Common ichidan verbs:

The Ambiguity: -ru Verbs That Are Actually Godan

The critical challenge: not all -iru/-eru verbs are ichidan. Some must be memorized as godan exceptions:

When kanji is visible, identification is unambiguous — the kanji spelling differs. In hiragana-only text, learners must recognize the verb by memory.

Conjugation Paradigm

Using taberu (食べる, to eat) as the example:

The key rule: The stem (tabe-) NEVER changes. Only the suffix is swapped. This is what “ichidan” (one-step) means — conjugation happens in one row/step.

Ichidan vs. Godan: Side-by-Side

Notice that godan verbs require learning which row the stem shifts to for each form. Ichidan verbs: just remove -ru and append. This is why ichidan is often taught first in textbooks — learners can build confidence with one predictable pattern before tackling godan complexity.

The Ra-nuki Phenomenon (ら抜き言葉)

In casual/colloquial modern Japanese, many speakers drop the ra from the potential form of ichidan verbs:

This ra-nuki kotoba (ら抜き言葉) is widely used in spoken Japanese, especially among younger speakers. It is considered informal/non-standard in written Japanese and formal contexts. For L2 learners, knowing about ra-nuki helps avoid confusion when encountering native speech — tabereru is NOT a separate word, just the casual potential form of taberu.

Acquisition Notes

Why ichidan is learned first:

The one-rule conjugation (remove -ru, add suffix) reduces cognitive load for beginners and allows mastery of the full paradigm with minimal memorization. Learners can then apply this knowledge analogically.

Overgeneralizing ichidan:

A very common L2 error is treating godan -ru verbs as ichidan:

• \kaette → should be kaette* (帰る is godan, so it undergoes double-t change, but the error is confusing it with ichidan change)
• \kite for kiru (切る, cut) → should be kitte (godan); though kiru (着る, wear) IS ichidan, giving kite*

Native speaker acquisition:

Children acquiring Japanese as an L1 also overgeneralize ichidan conjugation early (\kaimashira*-type forms disappear by school age), suggesting the regular pattern is cognitively dominant.

History

The ichidan/godan classification reflects the structure of Japanese verbal morphology documented in classical Japanese grammar. In traditional Japanese grammatical analysis (国文法, kokubunpō), verbs were categorized by the rows (dan) of the Japanese syllabary (kana table) their stem endings corresponded to — ichidan verbs (ichi = one) required only one row, while godan verbs (go = five) required five. This classification system was formalized in the Meiji era (late 19th century) as part of standardizing national language instruction, and it remains the standard pedagogical framework in Japanese grammar teaching. For learners of Japanese as a foreign language, the same underlying phonological distinction is now more commonly presented as ru-verbs (ichidan) vs. u-verbs (godan) based on the infinitive (dictionary form) ending.

Common Misconceptions

“Any verb ending in -ru is an ichidan verb.” This is one of the most common errors in Japanese learning: many godan verbs also end in -ru in their dictionary form — kiru (to cut, godan) vs. kiru (to wear, ichidan); kaeru (to return, godan) vs. kaeru (to change, ichidan). The -ru ending is necessary but not sufficient to identify an ichidan verb. Learners must learn exceptions explicitly, and the distinction is only reliable when combined with the preceding vowel (verbs ending in -iru and -eru are probably but not certainly ichidan).

“Ichidan verbs are ‘easier’ than godan verbs.” Ichidan verbs have simpler conjugation patterns but are not inherently easier — all verbs require the correct form to be retrieved accurately in production. The inflectional paradigm of ichidan verbs has fewer phonological changes, but beginners must still produce the correct register, politeness level, and grammatical form. The conjugation simplicity of ichidan verbs relative to godan only matters after learners understand the parallel paradigm structures.

Criticisms

Japanese language pedagogy has been criticized for presenting ichidan vs. godan as a binary classification that hides the complexity of identifying which class a given verb belongs to. The -ru/-non-ru heuristic taught at beginner level fails systematically for a significant minority of verbs, creating fossilized misclassifications. Some modern pedagogical approaches delay systematic verb conjugation study (teaching it through exposure to patterned input) rather than through early explicit classification instruction, arguing that classification rules before pattern recognition creates confusion.

Social Media Sentiment

Ichidan verbs and the ichidan/godan distinction are core Japanese beginner content — every general Japanese channel and subreddit covers the distinction early in the learning sequence. The common confusion over -ru ending godan verbs is a shared learning experience widely discussed in communities, with community members sharing mnemonic lists of “fake ru-verbs” that are actually godan. The elegant simplicity of ichidan conjugation is contrasted favorably with godan’s phonological consonant changes in community discussions of Japanese grammar.

Last updated: 2026-04

Practical Application

When encountering a new Japanese verb, look up its class alongside its meaning and record both — do not attempt to infer class from form alone. Building recognition of godan verbs ending in -ru (the exception class) through frequency exposure is more reliable than memorizing rules. At N5-N4 level, high-frequency ichidan verbs (taberu, miru, neru, okiru, kiru, iru, deru) should be mastered first. Sakubo presents vocabulary in contextual sentences — regular exposure to ichidan verbs in conjugated forms across naturalistic contexts supports internalization of the correct conjugation patterns without relying solely on explicit rule recall.

Related Terms

• Godan Verbs — the other main verb class
• Suru Verbs — the “to do” class
• Verb Conjugation — full system overview
• Inflectional Morphology — the linguistic framework
• Japanese Particles — grammatical markers
• JLPT N5 — level at which ichidan basics appear

See Also

• Godan Verbs
• Japanese Grammar
• Verb Conjugation
• JLPT

Research

Makino, S., & Tsutsui, M. (1986). A Dictionary of Basic Japanese Grammar. Japan Times.

The comprehensive reference grammar for Japanese learners and teachers, providing full conjugation paradigms for ichidan and godan verbs with example sentences — the standard pedagogical reference for Japanese verb morphology.

Shibatani, M. (1990). The Languages of Japan. Cambridge University Press.

A descriptive linguistics account of Japanese including full morphological analysis of the verb conjugation system — provides the theoretical linguistic description of ichidan verb morphology within the broader Japanese verbal paradigm.

Shirai, Y., & Andersen, R. W. (1995). The acquisition of tense-aspect morphology: A prototype account. Language, 71(4), 743-762.

A cross-linguistic study of tense-aspect morphology acquisition including Japanese verb morphology, examining how learners acquire verb inflection through frequency exposure and prototypical category learning — relevant for understanding how ichidan conjugation patterns are acquired.