kau-vs-uru

Every time money changes hands in Japanese, two verbs are at the center of the transaction: かう (kau) — to buy — and うる (uru) — to sell. These are antonyms and come up constantly in daily life, from shopping conversations to business negotiations. What makes them interesting for English learners is how they conjugate differently and how they interact with particles. Understanding both verbs opens up a wide range of practical Japanese you can use immediately.

Yuka

Rei, I’ve seen kau and uru so many times but I always second-guess myself. Help!

Rei

Don’t worry — this is one of the most common points of confusion for English speakers. Let me clear it up once and for all!

At a Glance: かう vs うる

かう (買う) — To Buy

かう is a Group 1 (う-verb) meaning “to buy” or “to purchase.” The kanji 買 contains the radical for “net” on top and “shell/money” on the bottom — historically, shells were used as currency, so the kanji literally suggests catching/acquiring money/goods. What you buy is marked with the particle を.

Conjugation highlight: The negative form is かわない (kawanai), not かいない — the stem changes from か to かわ before ない. This is a common point of confusion for beginners.

Example sentence 1:

スーパーで野菜を買いました。
Sūpā de yasai o kaimashita.
I bought vegetables at the supermarket.

Example sentence 2:

新しいスマホを買いたい。
Atarashii sumaho o kaitai.
I want to buy a new smartphone.

Example sentence 3:

この服はどこで買ったの？
Kono fuku wa doko de katta no?
Where did you buy these clothes?

Yuka

Okay, that example with kau really helped! I never saw it used that way before.

Rei

Right? Seeing real examples is so much more useful than memorizing a definition. kau is definitely one of those words you’ll start noticing everywhere.

うる (売る) — To Sell

うる is also a Group 1 (う-verb) meaning “to sell.” The kanji 売 can be thought of as showing a person (士) standing over a shell/money (貝) — someone offering something of value. What you sell is marked with the particle を.

Important note on うる vs うれる: うる (uru) is the active verb — you sell something. うれる (売れる, ureru) is the intransitive/potential form meaning “to sell well” or “to be sold.” You will see うれる frequently in everyday conversation: この本はよく売れている (This book is selling well).

Example sentence 1:

古い自転車を売りました。
Furui jitensha o urimashita.
I sold my old bicycle.

Example sentence 2:

このお店は何を売っているんですか？
Kono omise wa nani o utte iru n desu ka?
What does this shop sell?

Example sentence 3:

この商品はよく売れています。
Kono shōhin wa yoku urete imasu.
This product is selling well.

Yuka

And uru — is it used in formal situations, casual ones, or both?

Rei

Great observation! uru actually works in both — context is everything. The comparison table coming up should make this super clear.

Side-by-Side Comparison Table

Common Mistakes English Speakers Make

Mistake 1: Mixing up the negative stems
かう (kau) → negative: か + わない = かわない (NOT かいない). うる (uru) → negative: う + らない = うらない. Both verbs follow standard Group 1 (う-verb) conjugation rules, but the stem changes can surprise learners. Practice the negative forms separately until they feel automatic.

Mistake 2: Confusing うる (sell) with うれる (sell well / be sold)
うる is transitive — someone actively sells something. うれる is often used as an intransitive verb meaning the item “sells” on its own: この商品はよく売れる (This product sells well). The distinction matters for describing market performance vs. personal action.

Mistake 3: Forgetting で for location
Both verbs require で to mark the location of the transaction: コンビニで買う (buy at a convenience store), フリマで売る (sell at a flea market). Do not use に for location with these verbs — に marks the recipient when selling to someone (友達に売る = sell to a friend).

Decision Flowchart: かう or うる?

Use this flowchart to choose the right verb:

Who is receiving the item?
├─ You are receiving the item (paying money) → Use かう (買う)
│　　└─ Pattern: [place]で + [item]を + かう
└─ Someone else is receiving the item (you get money) → Use うる (売る)
　　　├─ Pattern: [item]を + うる
　　　└─ Selling to someone: [person]に + [item]を + うる

Quick Quiz

Yuka

I feel ready! Let’s see how well I really know kau and uru.

Rei

Let’s find out! Don’t peek at the answers until you’ve tried each one yourself.

Fill in the blank with the correct form of かう or うる. Answers below.

1. 昨日、コンビニでお弁当を___。(Yesterday, I bought a bento at the convenience store.) [past casual]

2. 古い本をフリマアプリで___つもりです。(I plan to sell my old books on a flea market app.) [dictionary form + つもり]

3. この商品はよく___ている。(This product is selling well.) [うれる form]

4. 新しいゲームを___たい！(I want to buy a new game!) [たい form]

5. 友達にスマホを___。(I sold my smartphone to a friend.) [past casual]

Answers:

1. 買った (katta) — Past casual form of かう.
2. 売る (uru) — Dictionary form used before つもりです.
3. 売れ (ure-) — うれている: intransitive form showing the item sells well.
4. 買い (kai-) — 買いたい: wanting to buy (かう → stem かい + たい).
5. 売った (utta) — Past casual form of うる.

かう and うる are everyday verbs that show up in shops, online marketplaces, and business conversations. With a solid grasp of their conjugations and the key particle patterns, you can handle any transaction-related conversation in Japanese confidently.

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