The Ta-Form in Japanese: Construction Rules

The construction rules for the Japanese ta-form come down to one decision: identify the verb's class, then attach た or だ to the right stem.^{1 2} If you already know the te-form, you get the whole pattern for free. The ta-form uses the same stem shapes, with た / だ in place of て / で.^{3 4}

Overview

What the ta-form is and is not

The ta-form (た形たけい, ta-kei) is the plain-style past affirmative of the Japanese verb. Its endings are た after voiceless clusters and だ after voiced ones.^{1 2 5 6}

The ta-form is finite: it carries tense. That distinguishes it from the morphologically parallel te-form, which is non-finite and carries no tense or politeness of its own.^{1 7 2}

The plain past is not polite by itself. The polite-past equivalent is built on the masu-form (V-ました), not by adding です to the ta-form.^{1 8 6}

The ta-form is affirmative only. The plain past negative is built on the nai-form (V-なかった), not by negating the ta-form.^{1 8 2}

Construction scope, not tense scope

This article covers how to build the ta-form. Tense, aspect, and special readings of the ta-form (discovery 「あった！」, soft command 「寝ねた寝ねた！」, and counterfactual ～たら-type uses) are covered in a separate treatment of the ta-form's uses.^{1 2}

The ta-form to te-form parallel

The ta-form is built by the same five godan cluster transformations as the te-form, with た / だ replacing て / で.^{1 2 9 5 6}

This is one piece of verb-shape knowledge shared between two paradigms. Both attach an auxiliary to the same 音便おんびん-modified stem; only the final kana (て vs た, で vs だ) differ.^{3 2 4}

The "te-form to ta-form swap" is not just a mnemonic shortcut. It is the literal historical and morphological fact: same stem, same cluster, different selecting morpheme (the ending that chooses て / で or た / だ).^{3 4}

Why the ta-form is taught early

The ta-form is introduced at N5 in every major beginner syllabus: Genki I Lesson 9⁸, Minna no Nihongo Lesson 19¹⁰, and the Bunpro N5 grammar library¹¹.

Genki places it immediately after the te-form (Lesson 6) and explicitly trades on the shared cluster rules.⁸

The ta-form unlocks later patterns that are themselves core N5 to N4 grammar: ～たことがある (experiential), ～たり…たりする (non-exhaustive enumeration), ～たら (conditional), ～たほうがいい (advice), and V-た + N (past relative-clause modification).^{1 8 2 6} A student who can produce the ta-form for any given verb can use all of these by lexical substitution.^{8 2}

Prerequisites and where this fits

You should already know the three verb classes (一段いちだん, 五段ごだん, irregular). Misclassification propagates: a learner who classifies 帰かえる as 一段 will produce *帰かえた instead of the correct 帰かえった.^{1 2 12}

You should also know the dictionary form, since the ta-form (like the te-form) is built from it, not from the masu-stem.^{1 2}

The iru/eru-godan trap (帰る, 切る, 走る, 入る, 知る, 要る) recurs here exactly as it does for the te-form, because it is the same cluster decision.^{1 2 12}

Construction rules by verb class

一段 (ichidan / ru-verbs): drop る, add た

For every 一段 verb, build the ta-form by removing the final る of the dictionary form and adding た. There are no exceptions in the modern teaching set.^{1 8 2 11 5 6 13}

The drop-る + た rule mirrors the te-form's drop-る + て rule one-to-one; only the selecting morpheme differs.^{1 2 5}

朝あさご飯はんを食たべた。⁸
"I ate breakfast."

朝あさ六時ろくじに起おきた。⁶
"I woke up at six in the morning."

昨日きのうその映画えいがを見みた。⁵
"I saw that movie yesterday."

Watch for godan verbs that end in -iru or -eru

A small set of common 五段 verbs end in -iru or -eru in their dictionary form, so they look like 一段 verbs on the surface. Their ta-form follows the godan る-cluster rule (→ った), not the 一段 drop-る rule (→ た).^{1 2 12} The high-frequency offenders to memorise by N5 are 帰る, 切る, 走る, 入る, 知る, and 要る.^{2 12}

五段 (godan / u-verbs): five transformation clusters

For 五段 verbs, the ta-form depends on the final kana of the dictionary form. It falls into one of five clusters: う/つ/る → った, む/ぶ/ぬ → んだ, く → いた, ぐ → いだ, す → した.^{1 8 2 11 5 6 13 14 15}

The clusters are identical to the te-form's, with た / だ substituting for て / で.^{1 2 9 4 5}

う / つ / る → った

Verbs whose dictionary form ends in う, つ, or る (godan -る only) all form their ta-form with the geminate った cluster. This is the 促音便そくおんびん (sokuonbin) outcome.^{1 2 16 4 11 5 6 13}

The る at this fork is godan-る (consonant stem -r), not 一段-る. A godan verb in -ru takes った; an ichidan verb in -る takes the simple drop-る + た rule above. This is the most common ta-form misclassification point.^{1 2 12}

リンゴを買かった。⁶
"I bought an apple."

友達ともだちを一時間いちじかん待まった。⁸
"I waited an hour for my friend."

その本ほんを取とった。⁵
"I took that book."

む / ぶ / ぬ → んだ

Verbs whose dictionary form ends in む, ぶ, or ぬ all form their ta-form with the nasal cluster んだ. The voiced だ reflects the nasal or voiced consonant of the underlying stem. This is the 撥音便はつおんびん (hatsuonbin) outcome.^{1 2 16 4 11 5 6 13}

The shared んだ outcome reflects the historical /N/ + voicing trigger common to m-stem, b-stem, and n-stem verbs in Late Old and Early Middle Japanese.^{3 4}

死ぬ is the only modern verb in -ぬ; the historical ナ行変格なぎょうへんかく class has otherwise disappeared. In practice, the cluster is a む / ぶ rule with 死ぬ as a single straggler.^{9 17}

毎朝まいあさコーヒーを飲のんだ。⁶
"I drank coffee every morning."

子供こどもたちは公園こうえんで遊あそんだ。⁵
"The children played in the park."

その木きは台風たいふうで死しんだ。⁶
"That tree died in the typhoon."

く → いた

Verbs whose dictionary form ends in く form their ta-form with いた: the く is dropped and replaced by い + た. This is the イ音便いおんびん (i-onbin) outcome.^{1 2 16 4 11 5 6 13}

行く is the lone exception to this rule and is treated under "不規則ふきそく" below.^{9 5 14 17}

名前なまえをここに書かいた。⁵
"I wrote my name here."

音楽おんがくを聞きいた。⁶
"I listened to music."

駅えきまで歩あるいた。⁶
"I walked as far as the station."

ぐ → いだ

Verbs whose dictionary form ends in ぐ form their ta-form with いだ: the ぐ is dropped and replaced by い + だ. The voicing on だ reflects the voiced stem-final /g/, mirroring the voiceless く → いた pattern. This is the same イ音便 outcome, but voiced.^{1 2 16 4 11 5 6 13}

Every modern verb in -ぐ is godan and takes いだ; no exceptions.^{9 11}

プールで泳およいだ。⁶
"I swam in the pool."

駅えきまで急いそいだ。⁵
"I hurried to the station."

玄関げんかんで靴くつを脱ぬいだ。¹⁰
"I took my shoes off at the entryway."

す → した

Verbs whose dictionary form ends in す form their ta-form with した: the す is replaced by し + た. The stem-final /s/ is preserved.^{1 2 11 5 6 13}

Unlike the other four clusters, this transformation is not an 音便 outcome. The s-stem stayed stable during the same period in which the other consonants underwent gemination, nasalisation, or palatalisation. The し here is the same 連用形れんようけい form that appears in the masu-form 話はなします.^{3 18 2 4}

Every modern verb in -す is godan and takes した; no exceptions.^{9 11}

友達ともだちと日本語にほんごで話はなした。⁸
"I spoke in Japanese with my friend."

ペンを貸かした。⁸
"I lent a pen."

ドアを押おした。⁵
"I pushed the door."

不規則 (irregular): する, 来る, 行く

The ta-form irregulars are する → した, 来る → 来た (きた), and 行く → 行った (いった). Treat 行く as irregular here even though it is otherwise a 五段 verb.^{1 8 2 11 5 6 13 14}

する → した uses the same し-stem visible in the masu-form (します) and the te-form (して). Every compound noun-する verb (勉強べんきょうする, 結婚けっこんする, 旅行りょこうする) inherits the した ta-form.^{1 19 5}

来る → 来た (きた, kita) shows the 来 kanji read as き-, matching the masu-form 来ます (きます) and the te-form 来て (きて). Every compound V-て + 来る verb (持もってくる, 出でてくる, 帰かえってくる) inherits this 来た.^{1 20 5}

行く → 行った (itta) is the only godan -く verb that does not follow the く → いた rule. Modern references treat this as a one-form lexical irregularity, not a fourth irregular class; the same exception applies to the te-form (行って, not *行いて).^{9 5 14 17}

行く does not take い-onbin

Applying the regular く → いた rule to 行く produces *行いた, which is not Japanese. The correct ta-form is 行った (itta), with the same 促音便 geminate that the て-form takes (行って).^{9 5 14 17}

今日きょうは宿題しゅくだいをした。¹⁹
"Today I did my homework."

友達ともだちが家いえに来きた。²⁰
"A friend came over."

銀行ぎんこうに行いった。⁶
"I went to the bank."

One-line te-form to ta-form swap rule

Universal shortcut: if you already have the te-form, replace て with た and で with だ. The rule covers every cluster, every irregular, and 行って → 行った.^{1 2 9 5 6}

This is a morphological fact, not only a learner heuristic: the te-form and the ta-form attach the same auxiliary stem to the same 連用形 + 音便; only the final selecting kana differs.^{3 2 4}

Class	Dictionary ending	Te-form ending	Ta-form ending	Example (dict)	Example (ta-form)
一段	-る (ichidan)	-て	-た	食べる	食べた
一段	-る (ichidan)	-て	-た	見る	見た
五段	-う / -つ / -る	-って	-った	買う / 待つ / 取る	買った / 待った / 取った
五段	-む / -ぶ / -ぬ	-んで	-んだ	飲む / 遊ぶ / 死ぬ	飲んだ / 遊んだ / 死んだ
五段	-く	-いて	-いた	書く	書いた
五段	-ぐ	-いで	-いだ	泳ぐ	泳いだ
五段	-す	-して	-した	話す	話した
不規則 (irreg)	する	して	した	する	した
不規則 (irreg)	来る	来て (きて)	来た (きた)	来る (くる)	来た (きた)
不規則 (irreg)	行く (五段, exception)	行って (いって)	行った (いった)	行く (いく)	行った (いった)

Nuance and usage contexts

Plain past versus polite past

The ta-form is the plain-style past affirmative. The polite-style equivalent is built on the masu-form: V-ました.^{1 8 2}

Both refer to the same past event; the choice tracks register, not tense.^{1 8 6}

Here are the same predicates in both registers: 食べた (plain) / 食べました (polite); 行った (plain) / 行きました (polite); した (plain) / しました (polite).^{1 8 19} A learner who can produce both forms can choose register independently from tense.^{1 8}

昨日きのう銀行ぎんこうに行いった。⁶
"I went to the bank yesterday." (plain)

昨日きのう銀行ぎんこうに行いきました。⁸
"I went to the bank yesterday." (polite)

Negative plain past is nai-form ～なかった, not ta-form

The ta-form is affirmative only. The plain past negative is built on the nai-form: V-ない → V-なかった (the い-adjective-style past inflection of ない).^{1 8 2}

Worked pairs: 食べる → 食べない → 食べなかった; 行く → 行かない → 行かなかった; する → しない → しなかった; 来る → 来ない (こない) → 来なかった (こなかった).^{1 8 2}

The ta-form and the nai-form handle two separate contrasts: tense and polarity. The ta-form covers past affirmative, while the nai-form's past inflection covers past negative.^{1 2}

The ta-form is the gateway to several downstream patterns

The following later patterns all attach to a correctly built ta-form. They are named here for orientation only; each is a separate topic.^{1 8 2 6}

• ～たことがある: experiential past ("have done X before").^{1 2}
• ～たり…たりする: non-exhaustive enumeration of past or characteristic actions.^{1 8 2}
• ～たら: past-conditional, "when / if" with a realised antecedent.^{1 2}
• ～たほうがいい: recommendation ("you'd better do X").^{1 8 2}
• V-た + N: past-tense relative clause modification (買った本, "the book I bought").^{1 2 6}

All five are core N5 to N4 grammar. Once you know the construction rules, you have the entry point to all of them.^{8 2}

Good to know

Why the godan clusters look exactly like the te-form clusters

The five godan ta-form clusters (った, んだ, いた, いだ, した) are historically identical to the five te-form clusters. Only the selecting auxiliary differs (た / だ instead of て / で).^{1 3 2 4}

Both the te-form and the ta-form attach to the same 連用形 (ren'yōkei) plus 音便-modified stem. The cluster shapes come from a single sound-change pathway in Late Old and Early Middle Japanese; they were not invented twice.^{3 4}

The four 音便 subtypes map to the ta-form clusters directly:^{2 16 4}

音便 subtype	Ta-form outcome	Mechanism
促音便 (sokuonbin)	geminate /Q/	stem-final /w/, /t/, /r/ + /ta/ → /Qta/ (った)
撥音便 (hatsuonbin)	nasal /N/	stem-final /m/, /b/, /n/ + /ta/ → /Nda/ (voiced んだ)
イ音便 (i-onbin)	/i/-vowel	/ki/ + /ta/ → /ita/; /gi/ + /ta/ → /ida/ (voiced いだ)
ウ音便 (u-onbin)	/u/-vowel	/Cu/ + /ta/ → /uta/ (Kansai-only in standard speech)

The す cluster resists 音便; the 連用形 し is preserved unchanged, parallel to the te-form's して.^{3 18 2 16 4}

The te-form to ta-form swap as a memory hook

Anywhere you wrote て, write た. Anywhere you wrote で, write だ. The rule is universal: it covers every godan cluster, every irregular, and the 行って → 行った exception.^{1 2 9 5 6}

This is also how you can turn the standard te-form song (う・つ・る → って…) into a ta-form version: swap the final kana in every line. The cluster choice and the irregulars list do not change.^{5 6}

行った is ambiguous between 行く (to go) and 言う (to say)

The surface forms 行った and 言った are both read itta; only the kanji marks the difference.^{9 21} A sentence like 彼は何も言った is not a construction error (godan う → った is regular), but a reading-comprehension trap for learners who meet 言った and 行った side by side in early reading. The intended meaning "He said nothing" is built on the negative past:

彼かれは何なにも言いわなかった。²¹
"He said nothing."

In speech, context and pitch disambiguate; in writing, the kanji does the work.²¹

The iru / eru-godan trap recurs

A small set of common 五段 verbs end in -iru or -eru in their dictionary form, so they look like 一段 verbs on the surface. Their ta-form follows the godan る-cluster rule (→ った), not the 一段 drop-る rule (→ た).^{1 2 12} The high-frequency offenders to memorise by N5 are 帰る, 切る, 走る, 入る, 知る, and 要る.^{2 12} Applying the 一段 rule to 帰る produces *帰た; the correct form is:

家いえに帰かえった。⁶
"I went home."

To separate 一段 from godan -iru/-eru, check the ない-form vowel: 帰る → 帰らない (/a/ before ない → godan); 食べる → 食べない (/e/ before ない → ichidan).^{1 2}

行く is the irregular learners forget

行く is godan in every modern reference, but its ta-form is 行った (itta), not the expected *行いた. It is the only godan -く verb that resists い-onbin.^{9 5 14 17} The same exception applies to the te-form (行って, not *行いて). The cluster mismatch is irregular, not the verb class. The correct form:

銀行ぎんこうに行いった。⁶
"I went to the bank."

Treating 行く as a first-class irregular in the rule table, alongside する and 来る, prevents the regularised error.^{5 17}

あった and いた are not exceptions

ある → あった is a regular godan -る → った application (sokuonbin). The verb is morphologically godan, not irregular; the modern teaching tradition flags it only because it is the most common verb and its negative (ない) is suppletive, not its past.^{1 2 9}

いる → いた is a regular ichidan drop-る + た application. The verb is morphologically ichidan; its past is a textbook drop-る case.^{1 2} Both surface forms are common enough that beginners sometimes mark them as irregular. They are not. They are textbook applications of the cluster rules.^{1 2 9}

The selecting kana (た vs だ) is conditioned by the cluster

The ta-form ends in either た (voiceless) or だ (voiced). The split is determined by the cluster, not by meaning, politeness, or context. った, いた, and した end voiceless; んだ and いだ end voiced.^{2 16 4}

The voicing of だ reflects the underlying stem-final consonant (nasal /m/, /n/, /b/, or voiced /g/) carrying its voicing into the suffix, exactly as in the te-form's で.^{3 2 4}

Small っ versus full つ in った

The geminate cluster った uses the small っ (sokuon), not the full つ. Learners typing in an IME (input method editor) sometimes accept the full-size つ from the first candidate and produce つた (two morae). That is not a valid form for any verb in this paradigm.^{5 6} Applying the rule to 買う gives 買った (katta), not the incorrect 買つた:

リンゴを買かった。⁶
"I bought an apple."

In IME input, typing the doubled consonant (katta → かった) produces the small っ automatically. The typing fix is to type the double consonant directly rather than to pick つ from a candidate list.⁵ The equivalent check for the nasal cluster is simpler: んだ uses the moraic ん, which is its own character and cannot be confused with な-row kana.¹⁶

See also

• The Plain Past た-Form in Japanese: Past, Perfective, and Beyond
• The Te-Form in Japanese: Construction Rules
• Japanese Verb Groups: 一段, 五段, and Irregular
• The Nai-Form (ない形): Plain Negative of Japanese Verbs
• The Masu Form (ます): Polite Present and Future Tense
• The Japanese Verb Stem (連用形): The Masu-Stem and Its Uses

References

Footnotes

1. Makino, Seiichi, and Michio Tsutsui. A Dictionary of Basic Japanese Grammar. The Japan Times, 1986. ISBN 978-4-7890-0454-1. Entry "ta-form" and the verb-class conjugation tables, pp. 478–482 and pp. 582–595. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹ ↩³⁰ ↩³¹ ↩³² ↩³³ ↩³⁴ ↩³⁵ ↩³⁶ ↩³⁷ ↩³⁸ ↩³⁹ ↩⁴⁰ ↩⁴¹ ↩⁴² ↩⁴³ ↩⁴⁴ ↩⁴⁵ ↩⁴⁶

2. 庵功雄・松岡弘・中西久実子 ほか (Iori, Isao, et al.). 『初級を教える人のための日本語文法ハンドブック』(A Handbook of Japanese Grammar Patterns for Teachers of Beginning-Level Japanese). スリーエーネットワーク, 2000. ISBN 978-4-88319-148-0. Chapter on the ta-form, its formation rules by class, and the 音便 framing shared with the te-form. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹ ↩³⁰ ↩³¹ ↩³² ↩³³ ↩³⁴ ↩³⁵ ↩³⁶ ↩³⁷ ↩³⁸ ↩³⁹ ↩⁴⁰ ↩⁴¹ ↩⁴² ↩⁴³ ↩⁴⁴ ↩⁴⁵ ↩⁴⁶ ↩⁴⁷ ↩⁴⁸ ↩⁴⁹ ↩⁵⁰ ↩⁵¹

3. Frellesvig, Bjarke. A History of the Japanese Language. Cambridge University Press, 2010. ISBN 978-0-521-65320-6. Chapters on Late Old Japanese and Early Middle Japanese sound change, including the rise of 音便 (onbin) and the geminate, nasal, and i-onbin reflexes in -te / -ta formation. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

4. Wikipedia contributors. "五段活用" (Godan katsuyō). Wikipedia, The Free Encyclopedia. https://ja.wikipedia.org/wiki/五段活用 (limitation: encyclopedic reference; used for the godan paradigm description and the historical onbin description applied to past-tense た / だ formation). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷

5. Tofugu. "Japanese Verb Plain Past た Form." https://www.tofugu.com/japanese-grammar/verb-past-ta-form/ (limitation: language-learning publisher; used for the cluster-by-cluster construction rules of the ta-form and the te-form-to-ta-form swap framing). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹ ↩³⁰

6. Wasabi. "Past Tense and Present Perfect Tense with the Ta-form." https://wasabi-jpn.com/magazine/japanese-grammar/past-tense-and-present-perfect-tense-with-the-ta-form/ (limitation: language-learning publisher; used for the standard learner-facing ta-form construction table and the te-to-ta swap mnemonic). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹ ↩³⁰ ↩³¹

7. Vance, Timothy J. An Introduction to Japanese Grammar and Communication Strategies. The Japan Times, revised edition, 1993. ISBN 978-4-7890-0698-9. Consonant-stem / vowel-stem treatment of godan and ichidan verbs and their non-finite -te / -ta inflection. ↩

8. Banno, Eri, et al. Genki I: An Integrated Course in Elementary Japanese, 3rd edition. The Japan Times, 2020. ISBN 978-4-7890-1730-5. Lesson 9 introduces the plain past ta-form with the full godan/ichidan/irregular construction table and the te-form-to-ta-form parallel. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴

9. Wikipedia contributors. "Japanese verb conjugation." Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/wiki/Japanese_verb_conjugation (limitation: encyclopedic reference; used for the cross-paradigm summary of the -te / -ta onbin allomorphy and the listing of 行く as the single irregular godan -ku verb). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴

10. 3A Corporation. 『みんなの日本語 初級I 第2版』(Minna no Nihongo Shokyū I, 2nd ed.). スリーエーネットワーク, 2012. ISBN 978-4-88319-603-4. Lesson 19 introduces the plain past ta-form alongside ～たことがある and ～たり. ↩ ↩²

11. Bunpro. "Verbs - Past Form (JLPT N5)." https://bunpro.jp/grammar_points/verb-past (limitation: language-learning publisher; used for the canonical N5-level ta-form construction rules: う/つ/る → った, む/ぶ/ぬ → んだ, く → いた, ぐ → いだ, す → した, ichidan る → た, する → した, 来る → 来た, 行く → 行った). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

12. sljfaq.org. "How does the te form work?" https://www.sljfaq.org/afaq/te-form.html (limitation: community FAQ; used for the cluster-by-cluster construction rules shared between te and ta, and the explicit flagging of 行く as a one-form irregularity). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

13. Practice Japanese. "Ta-form (Plain Past)." https://practice-japanese.com/docs/verb-ta-form/ (limitation: language-learning publisher; used for the standard learner-facing ta-form construction table covering the five godan clusters and the three irregulars). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

14. University of Texas at Austin, JOSHU project. "Conjugation: Ta-form." https://laits.utexas.edu/japanese/joshu/conjugation/conref/cr_taform.php (used for the ta-form rule table and the explicit "exception" labelling of 行く → 行った). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

15. Punipuni Japan. "Japanese Grammar: Plain Past Verbs (Ta-Form)." https://www.punipunijapan.com/japanese-ta-form/ (limitation: language-learning publisher; used as a third independent confirmation of the standard learner-facing ta-form cluster table). ↩

16. Wikipedia contributors. "Onbin." Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/wiki/Onbin (limitation: encyclopedic reference; used for the inventory of the four onbin subtypes (イ音便, ウ音便, 撥音便, 促音便) and the sound-change descriptions tied to -te / -ta formation). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

17. Wikipedia contributors. "Japanese irregular verbs." Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/wiki/Japanese_irregular_verbs (limitation: encyclopedic reference; used for the listing of 行く as the sole godan -ku verb with an irregular sokuon-style te / ta-form). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

18. Shibatani, Masayoshi. The Languages of Japan. Cambridge University Press, 1990. ISBN 978-0-521-36918-3. Chapter 7 covers verbal morphology, the -te / -ta paradigm, and the onbin-driven allomorphy of consonant-stem verbs. ↩ ↩²

19. Bunpro. "する (JLPT N5)." https://bunpro.jp/grammar_points/%E3%81%99%E3%82%8B (limitation: language-learning publisher; used for the irregular paradigm of する at N5, including した). ↩ ↩² ↩³

20. Bunpro. "くる (JLPT N5)." https://bunpro.jp/grammar_points/%E3%81%8F%E3%82%8B (limitation: language-learning publisher; used for the reading shifts of 来る at N5, including 来た (きた)). ↩ ↩²

21. 大辞林 (Daijirin), 第三版. 三省堂. Entries 「言う」 (iu) and 「行く」 (iku) showing the surface form 「言った」/「行った」 both read itta. ↩ ↩² ↩³