Godan verbs whose dictionary form ends in ぐ build the te-form as いで: 泳ぐ (oyogu) → 泳いで (oyoide). This is one of the smallest verb groups in the language, and it is the exact twin of the く group — with one crucial difference. Because ぐ is a voiced sound, the connector voices too, giving you で rather than て. Miss that voicing and you have made a genuine error, not a typo.
The rule in one line
Drop the final ぐ, and attach いで.
| Dictionary form | te-form | Reading |
|---|---|---|
| 泳ぐ (to swim) | 泳いで | oyogu → oyoide |
| 急ぐ (to hurry) | 急いで | isogu → isoide |
| 脱ぐ (to take off / remove clothing) | 脱いで | nugu → nuide |
| 稼ぐ (to earn money) | 稼いで | kasegu → kaseide |
| 騒ぐ (to make noise) | 騒いで | sawagu → sawaide |
| 防ぐ (to prevent) | 防いで | fusegu → fuseide |
海で泳いで、そのあと砂浜で昼寝した。
umi de oyoide, sono ato sunahama de hirune shita
I swam in the sea and then took a nap on the beach.
急いで！電車、もう来るよ。
isoide! densha, mō kuru yo
Hurry up! The train's coming already.
玄関で靴を脱いでください。
genkan de kutsu o nuide kudasai
Please take off your shoes at the entrance.
Why it voices: the logic behind いで
The change here is the same イ音便 (i-onbin) you already met with く-verbs like 書く → 書いて. Historically the te-form attached to the ます-stem (連用形): 泳ぎ + て. The ぎ was awkward to say before て at speed, so it softened into the vowel い. That gives you the いて / いで shape.
The remaining question is only: does the connector stay unvoiced (て) or voice (で)? And here Japanese is perfectly consistent. The final kana of the dictionary form tells you everything:
- く ends in an unvoiced k-sound → 書いて (kaite), unvoiced connector.
- ぐ ends in a voiced g-sound → 泳いで (oyoide), voiced connector.
The voicing of the verb's own ending simply carries through into the connector. You are not memorizing an extra fact — you are hearing the g of ぐ ring on into で.
It runs exactly parallel to く
Line the two groups up and the pattern is unmistakable. Everything is identical except the single voicing mark (the dakuten ゛).
| く-verb | te-form | ぐ-verb | te-form |
|---|---|---|---|
| 書く (to write) | 書いて | 泳ぐ (to swim) | 泳いで |
| 聞く (to listen) | 聞いて | 急ぐ (to hurry) | 急いで |
| 歩く (to walk) | 歩いて | 脱ぐ (to take off) | 脱いで |
If you can already form 書いて, you already know how to form 泳いで — just add the dakuten and let it voice.
夏休みは実家でずっとバイトして、けっこう稼いでいたよ。
natsu-yasumi wa jikka de zutto baito shite, kekkō kaseide ita yo
Over summer break I worked part-time at my parents' place the whole time and earned quite a bit.
今プールで泳いでいます。あとで折り返します。
ima pūru de oyoide imasu. ato de orikaeshimasu
I'm swimming in the pool right now. I'll call you back later.
Comparison with English
English has nothing that behaves like this. When we say "swim → swam" the change is stored in the word itself as an irregular past. Japanese onbin is different: it is a live sound-adjustment at the seam where two pieces join, and it applies by the sound of the ending, not by the individual verb. Every ぐ-verb behaves the same way, with no lists to memorize — the phonetics do the sorting for you. Once you internalize "voiced ending → voiced connector," you can produce the te-form of a ぐ-verb you have never seen before, correctly, on the first try.
子供たちが二階で騒いでいて、全然集中できない。
kodomo-tachi ga nikai de sawaide ite, zenzen shūchū dekinai
The kids are making a racket upstairs and I can't concentrate at all.
暑いから、上着を脱いでもいいですか。
atsui kara, uwagi o nuide mo ii desu ka
It's hot, so may I take off my jacket?
How many ぐ-verbs are there, really?
Honestly, not many. Verbs ending in ぐ are one of the rarest godan groups, so your working list is short: 泳ぐ (swim), 急ぐ (hurry), 脱ぐ (undress), 稼ぐ (earn), 騒ぐ (make noise), 防ぐ (prevent), 注ぐ (pour), 繋ぐ (connect / tie), 担ぐ (carry on the shoulder). That is close to the complete set of everyday ones. Learn those nine and you have effectively mastered the group. This is the good news of the ぐ class: tiny membership, one rule, no exceptions.
風邪を防ぐために、手をよく洗ってね。
kaze o fusegu tame ni, te o yoku aratte ne
Wash your hands well to prevent catching a cold.
Common mistakes
❌ 海で泳いて、日焼けした。
umi de oyoite, hiyake shita
Incorrect — ぐ voices, so the connector must be で, not て.
✅ 海で泳いで、日焼けした。
umi de oyoide, hiyake shita
I swam in the sea and got sunburned.
The single most common English-speaker error is writing ×泳いて by careless analogy with 書いて. Both come from イ音便, but 書く is unvoiced and 泳ぐ is voiced — the dakuten is not optional decoration, it is the difference between right and wrong.
❌ 急って、駅まで走った。
isotte, eki made hashitta
Incorrect — ぐ never doubles into って; that's the う・つ・る pattern.
✅ 急いで、駅まで走った。
isoide, eki made hashitta
I hurried and ran to the station.
Do not borrow the っ (small tsu) from the う・つ・る group. ぐ softens to い, it does not double.
❌ コートを脱ぎて、椅子に掛けた。
kōto o nugite, isu ni kaketa
Incorrect — the raw ます-stem 脱ぎ never attaches straight to て.
✅ コートを脱いで、椅子に掛けた。
kōto o nuide, isu ni kaketa
I took off my coat and hung it on the chair.
The stem-plus-て form (×脱ぎて) is exactly the unsmoothed shape that onbin exists to replace. The language will always take the shortcut: 脱いで.
Key takeaways
- ぐ → いで. Drop ぐ, attach いで.
- It is the く pattern with the connector voiced to で, because ぐ is voiced.
- The voicing rule is universal: voiced endings (ぐ・ぶ・む・ぬ) → で; unvoiced endings → て.
- Never write ×泳いて and never double it to ×泳って.
- The group is tiny — 泳ぐ, 急ぐ, 脱ぐ, 稼ぐ and a handful more cover almost all daily use.
- Same change as the ぐ → いだ past: just swap だ for で.
Now practice Japanese
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Start learning Japanese→Related Topics
- Godan く → いて (and 行く → 行って)N4 — The く te-form group: godan verbs ending in く soften to いて via the i-vowel change (イ音便) — 書く→書いて, 聞く→聞いて — with the one high-frequency exception you must memorize, 行く→行って.
- Godan む・ぶ・ぬ → んでN4 — The second godan te-form group: verbs ending in む, ぶ, or ぬ take the nasal change (撥音便) to form んで — and crucially the connector voices from て to で: 読む→読んで, 遊ぶ→遊んで, 死ぬ→死んで.
- The te-form Song: All Rules on One PageN4 — The complete te-form system on a single page, built around the classic learner mnemonic — う・つ・る→って, む・ぬ・ぶ→んで, く→いて, ぐ→いで, す→して, plus ichidan and the two irregulars.
- The て/た Parallel: One Machinery, Two FormsN4 — The plain past た-form uses exactly the same sound-changes as the て-form — learn one and you get the other for free, along with the たら conditional and たり listing.