Au: Meet, Match, Fit, and Run Into Trouble

Three kanji, one sound

There is a single image under all three kanji: two things coming together. In 会う the two things are people, so the verb means meet. In 合う they are shapes, sizes, opinions or numbers, so the verb means fit, match or be correct. In 遭う one of them is misfortune arriving at you, so the verb means run into something bad. Once you hold that picture, the vocabulary stops looking like coincidence.

Grammatically au is a godan verb ending in u, and it conjugates the same way in every sense: aimasu, aimashita, awanai, atte, atta, and the potential aeru. Learners sometimes stumble on the te form, because the u drops and a small tsu appears: 会って atte, not aute. The past atta is identical in sound to the past of aru, so context and particles keep them apart.

There is also a transitive partner, awaseru, built from 合う. It means to make things match, and it appears everywhere: tokei o awasemasu for setting a watch, chikara o awasemasu for joining forces, kao o awasemasu for meeting face to face. If a sentence has a person deliberately aligning two things, awaseru is usually the verb you want, not au.

The sense table

The particle column is the fastest way to tell the senses apart in speech, where no kanji is visible. A person marked with ni before au is a meeting; a thing marked with ga before au is a match; a misfortune marked with ni is 遭う. If you can hear the particle, you have already understood the sentence.

Meeting people with 会う

会う takes ni for the person, and the place takes de: eki de tomodachi ni aimasu. To is also possible and shifts the feeling toward a mutual arrangement, which is why to au often turns up with plans and ni au with someone you happened to see. Both are natural; ni is the safer habit while you are building fluency, and it is the only choice when the other person is senior to you.

Two related verbs are worth adding early. Deau means to come across someone or something, including a book or an idea, and it carries a hint of significance: tabisaki de omoshiroi hito ni deaimashita. Battari plus au is the everyday way to say you bumped into someone unexpectedly, and the negative atte imasen is how Japanese expresses not having seen someone for a while.

Polite and humble ways to say you met

In business Japanese, plain aimashita about a client sounds blunt. The humble o-ai suru lowers your own action, and o-me ni kakaru lowers it further; the latter is literally to be placed before someone's eyes, and it is the phrase to use with a company president or an important guest. When you are talking about the listener's meeting rather than your own, switch to the respectful o-ai ni naru.

The frame around the verb carries the register, so the same event can be said three ways: aimashita among friends, o-ai shimashita to a client, o-me ni kakarimashita to someone considerably senior. The honorifics guide covers the wider system, but this one verb is worth drilling because introductions come first in every business relationship.

Matching, fitting and suiting with 合う

合う describes two things agreeing in shape, size, taste or purpose. The item that does the matching takes ga, and the thing it matches against takes ni: kono kutsu wa watashi no ashi ni aimasen. When no second item is mentioned, ga alone is enough, which is why a fitting room sentence is simply saizu ga aimasen.

The suiting sense is broad and very useful. A job can suit you, a climate can suit you, a wine can suit a dish. Note that clothes looking good on a person is not 合う but niau, a frozen compound covered further down; kono fuku wa watashi ni aimasen means it does not fit, while niaimasen means it does not look right on me. Getting those two apart saves a lot of confusion in shops.

Ki ga au and the social senses

A cluster of high-frequency expressions uses 合う to describe people matching each other. Ki ga au means you get on, hanashi ga au means you have things to talk about, shumi ga au means your interests overlap, and iken ga au means you agree. All of them take ga for the thing that matches, and the other person is marked with to: kare to wa ki ga aimasu.

These are the sentences that make small talk work, because they let you say why you like someone without sounding formal. The negative is equally useful and much softer than a direct criticism: iken ga aimasen deshita reports a disagreement without blaming anyone, which is exactly the tone a Japanese workplace prefers.

Answers, clocks and figures that are correct

合う also means being correct, in the sense of tallying with reality. An answer, a total, a receipt and a clock can all match or fail to match. The stative atte imasu is the normal form here, because you are describing a current state rather than a moment of matching: kono kotae wa atte imasu ka.

When a person does the aligning, switch to awaseru. Tokei o awasemasu means you set the watch; tokei ga atte imasu means the watch is showing the right time. This transitive and intransitive pairing works the same way as many other Japanese verb pairs, and the transitive and intransitive verb guide gives the wider pattern if you want to generalise it.

遭う: running into trouble

遭う is the sense learners most often produce wrongly, usually by reaching for a passive form. Japanese prefers jiko ni aimashita to a passive construction, and the thing that happens to you takes ni: ame ni au, suri ni au, taifū ni au. The verb already carries the sense that you were on the receiving end, so no extra grammar is needed.

The strongest member of the family is me ni au, where me means an experience rather than an eye. Hidoi me ni aimashita is the standard way to say you had an awful time of it, and it takes an adjective in front: taihen na me ni au, kowai me ni au. It is common in everyday speech and useful whenever you tell the story of a bad day.

The ~au suffix: doing something to each other

Au attaches to the masu stem of another verb and adds the meaning of doing that action mutually. The rule is mechanical: take the stem, drop masu, add au, and treat the result as a godan verb. Hanasu gives hanashiau, shiru gives shiriau, tasukeru gives tasukeau, mitsumeru gives mitsumeau. Because the action goes both ways, these verbs need two or more participants, and the group is usually marked with de or to.

This is one of the most productive patterns in the language, so recognising it saves you from looking up dozens of entries. When you meet an unfamiliar verb ending in au, split off the last syllables and ask whether the first half is a verb stem you know. If it is, the meaning is almost always that action performed reciprocally.

Tsukiau deserves a note of its own. With a person and a time span it means to be dating, and with a task it means to keep someone company, so kaimono ni tsukiatte kuremasen ka simply asks a friend to come shopping with you. Context, not the verb, decides which one a listener hears.

Machigau, niau, maniau and the frozen compounds

Three compounds look like the reciprocal pattern but are not, and they are among the most used words in the language. Niau means to suit someone, and the person takes ni: sono shatsu wa anata ni niatte imasu. Ma ni au means to be in time, with the deadline or the train marked by ni. Machigau means to be wrong, and its partner machigaeru is what you use when you mistake one thing for another.

Keep machigau and machigaeru apart by asking who is doing what. Kono kotae wa machigatte imasu says the answer is wrong, describing a state. Bangō o machigaemashita says I dialled the wrong number, describing your action. Learners tend to overuse machigaimashita for their own errors, where a native speaker would say machigaemashita or, in casual speech, machigaechatta.

Mistakes to avoid

• Marking the person you meet with o. 会う takes ni or to: tomodachi ni aimasu, never tomodachi o aimasu.
• Using a passive form for accidents. Say jiko ni aimashita rather than building a passive; the verb already means it happened to you.
• Mixing up au and niau in shops. Saizu ga aimasen is about fit; niaimasen is about how it looks on you.
• Saying ma ni aimashita as maniaimashita in writing without the ni. It is three parts, ma ni au, and the ni never disappears.
• Building a reciprocal compound with only one participant. Hanashiaimasu needs at least two people, so hitori de hanashiaimasu is not a sentence.
• Forgetting the small tsu in the te form. It is atte and atta, never aute or auta.