タメ口 (tameguchi) is casual, plain-form Japanese — how you talk with friends, family, and peers. To switch into it: turn ます verbs into plain forms (食べます → 食べる), drop です or change it to だ, ask questions with a rising tone instead of か (行きますか → 行く？), and add casual endings like よ, ね, じゃん, の. Use it only once a relationship allows it — start polite, switch down later.
Textbooks have a dirty secret: they teach you to be polite, and only polite. Years of です and ます later, you can navigate a job interview — but when a Japanese friend invites you to dinner, you still sound like you’re filling out a form. They notice. Stiff keigo with a close friend doesn’t read as “respectful”; it reads as distance.
The fix is タメ口 — casual speech. The name comes from タメ (slang for “same,” as in same age/rank) + 口 (“mouth/speech”): the way equals talk to equals. This guide is the conversion manual textbooks never gave you, plus the social rules for when to flip the switch.
Polite vs Plain: The Same Sentence, Two Registers
Polite: 明日映画を見に行きますか。
あしたえいがをみにいきますか。
Casual: 明日映画見に行く？
あしたえいがみにいく？
“Wanna go see a movie tomorrow?” — same meaning. Notice the casual version drops を, drops か, and ends on a rising tone.
Step 1: Convert the Verb Endings
The backbone of tameguchi is plain (dictionary) verb form instead of ます. Here’s the core map:
| Polite | Casual (plain) | Meaning |
|---|---|---|
| 食べます | 食べる | eat |
| 食べません | 食べない | don’t eat |
| 食べました | 食べた | ate |
| 食べませんでした | 食べなかった | didn’t eat |
| 行きます | 行く | go |
| 行きました | 行った | went |
Good news: plain form isn’t new grammar — it’s the dictionary form you already learned for connecting clauses (before と, と思う, から, etc.). Tameguchi just lets that plain form stand at the end of the sentence instead of hiding in the middle.
Step 2: Handle です and Adjectives
| Polite | Casual | Note |
|---|---|---|
| 学生です | 学生だ / 学生 | だ is often dropped, especially by women |
| 高いです | 高い | i-adjectives just drop です |
| 静かです | 静かだ / 静か | na-adjectives use だ or nothing |
| 元気でした | 元気だった | past of だ is だった |
Don’t add だ to i-adjectives! 高いだ is wrong. Casual is just 高い (or 高いよ / 高いね). The だ only attaches to nouns and na-adjectives.
Step 3: Casual Questions (Drop か)
In tameguchi you almost never use か. A question is marked by a rising tone, sometimes plus の.
| Polite question | Casual question | Meaning |
|---|---|---|
| 行きますか？ | 行く？ | You going? |
| 食べましたか？ | 食べた？ | Did you eat? |
| どうしてですか？ | どうして？/ なんで？ | Why? |
| 大丈夫ですか？ | 大丈夫？ | You okay? |
明日ひま？映画見に行かない？
あしたひま？えいがみにいかない？
“Free tomorrow? Wanna go see a movie?” — the negative 行かない？ is a friendly way to invite (“won’t you go?”), softer than 行く？
Step 4: Casual Sentence Endings
Plain form alone can sound blunt or robotic. Casual endings add the warmth and personality that make tameguchi feel friendly.
| Ending | Reading | Feeling |
|---|---|---|
| 〜よ | yo | Informing (“you know, FYI”): いいよ (it’s fine) |
| 〜ね | ne | Seeking agreement: そうだね (yeah, right?) |
| 〜じゃん | jan | “Right? / isn’t it?” — casual confirmation: いいじゃん！ |
| 〜の？ | no? | Soft question: どうしたの？ (what’s up?) |
| 〜だろ / 〜でしょ | daro / desho | “Right? / I bet” |
| 〜かな | kana | “I wonder…”: 行こうかな |
「これ、めっちゃおいしいじゃん！」「だよね、また来たいね。」
「これ、めっちゃおいしいじゃん！」「だよね、またきたいね。」
“This is super good, right?!” “Right? Let’s come again.” — めっちゃ (super) and じゃん are pure casual energy.
Step 5: The Contractions That Make You Sound Real
Spoken casual Japanese compresses constantly. Learn these and your ear (and mouth) level up instantly.
| Full form | Casual contraction | Meaning |
|---|---|---|
| 〜ている | 〜てる | 食べてる (eating) |
| 〜てしまう | 〜ちゃう | 忘れちゃう (end up forgetting) |
| 〜なければ | 〜なきゃ | 行かなきゃ (gotta go) |
| 〜という | 〜って | マナって言うんだ (called Mana) |
| 〜ては | 〜ちゃ | 見ちゃだめ (don’t look) |
| すごく | すごい / めっちゃ | very / super |
The Social Rules: When to Switch (and When NOT To)
This is where tameguchi gets dangerous for learners. Casual speech with the wrong person is genuinely rude — like calling a stranger’s grandmother by her first name. Use this map:
| Person | Register |
|---|---|
| Close friends, partner, siblings | Tameguchi (casual) |
| Peers your age, once you’ve clicked | Casual, after a polite start |
| Younger people / juniors (後輩) | Often casual, but read the room |
| Seniors (先輩), teachers, bosses | Polite — stay in です/ます |
| Strangers, customers, clients | Polite / keigo |
The golden rule: start polite, switch down on invitation. Japanese friends will often signal the shift: タメ口でいいよ (“casual’s fine”) or 敬語じゃなくていいよ (“you don’t need keigo”). Wait for that green light, or offer it yourself: タメ口で話そう？ (“wanna talk casually?”).
The Trap: Knowing Both, Switching Smoothly
Here’s the real challenge. It’s not enough to know plain form on a worksheet — you have to flip registers live, mid-conversation, without freezing. Most learners can produce one register but stall when they need to switch, because they only ever drilled the polite one.
The cure is exposure to real casual Japanese — the way friends actually talk — not just textbook dialogues. In Kanjijo, grammar is taught with both registers side by side: the full grammar bank shows you plain form and its polite twin together, so you learn the switch, not just one half. Casual structures and contractions ride one SRS engine with exclusive mnemonics, and the JLPT listening track exposes you to natural, casual conversation at native speed so じゃん, 〜てる, and なきゃ stop sounding foreign. Reading manga? Point the OCR scanner at a speech bubble and decode the casual line on the spot.
Related Reading on Kanjijo
Frequently Asked Questions
Tameguchi (タメ口) is casual, plain-form Japanese — how you speak with close friends, family, and peers. It drops です/ます and keigo for plain verb forms and casual endings like だよ, じゃん, and の. With the right person it signals closeness; with the wrong person it can sound rude.
Convert ます verbs to plain dictionary or plain-past form (食べます → 食べる, 行きました → 行った), replace です with だ or drop it, and turn か-questions into rising-tone plain form (行きますか → 行く?). Adjectives drop です (高いです → 高い). Add endings like よ, ね, じゃん, or の to set the tone.
With close friends, family, partners, and peers once a relationship is established. Stay polite with strangers, customers, teachers, bosses, and seniors until they invite casual speech (タメ口でいいよ). When unsure, start polite — switching down later is safe; starting too casual can offend.
No. Plain form (普通形) is just the casual register, neither polite nor rude by itself. It’s rude only when used with someone who expects politeness. Among friends it’s normal and warm — and stiff keigo with close friends can actually feel cold. Rudeness is about matching the form to the relationship.
Learn Both Registers with Kanjijo
Sounding natural means switching between polite and casual on the fly — not memorizing one half. Kanjijo’s full grammar bank teaches plain and polite forms together, one SRS engine and exclusive mnemonics lock in casual structures, and native-speed JLPT listening plus OCR manga scanning expose you to real タメ口 — all on a complete N5–N1 path with reading, vocabulary and mock tests.
Download Kanjijo FreeFinal Word
Polite Japanese gets you through the door; tameguchi gets you invited back. Learn to drop the ます, flatten です to だ, ask with a rising tone, and sprinkle じゃん and ね — then read the relationship before you switch. Do it right and your Japanese friends will finally feel like friends, not interviewers. 頑張ってね！