Expressing Uncertainty in Japanese Language

A doubtful man is uncertain whether or not to buy something at Kyoto market, southern Honshu

Ernst Haas / Getty Images

Most English speakers are probably not familiar with the subjunctive, as it only appears very rarely there. However, speakers of Spanish or French know it well, because they communicate theoretical ideas with "if," "might," or "maybe" by conjugating subjunctive verb forms. While there is no subjunctive mood or verb form in Japanese, there are several ways to express uncertainty. Related concepts when learning the language include the conditional or potential.

Darou, Deshou, and Tabun

Darou is a plain form of deshou, and means "will probably." The adverb tabun ("perhaps") is sometimes added.

Kare wa ashita kuru deshou.
彼は明日来るでしょう。
"He will probably come tomorrow."
Ashita wa hareru darou.
明日は晴れるだろう。
"It will be sunny tomorrow."
Kyou haha wa tabun uchi ni iru deshou.
今日母はたぶんうちにいるでしょう。
"My mother will probably be home today."

Darou or deshou are also used to form a tag question. In this case, you usually can tell the meaning from the context.

Tsukareta deshou.
疲れたでしょう。
"You were tired, weren't you?"
Kyou wa kyuuryoubi darou.
今日は給料日だろう。
"Today is a payday, isn't it?"

Ka, Kashira, Kana, and Kamoshirenai

Darou ka or deshou ka are used when guessing with doubt. Kashira is used only by females. A similar expression used by both genders is kana, though it is informal. These expressions are close to "I wonder" in English.

Emi wa mou igirisu ni itta no darou ka.
エミはもうイギリスに行ったのだろうか。
"I wonder if Emi has already gone to England."
Kore ikura kashira.
これいくらかしら。
"I wonder how much this is."
Nobu wa itsu kuru no kana.
のぶはいつ来るのかな。
"I wonder when Nobu will come."

Kamoshirenai is used to express a sense of probability or doubt. It shows even less certainty than darou or deshou. It is used when you don't know all the facts and are often just guessing. It is similar to the English expression "might be." The formal version of kamoshirenai is kamoshiremasen.

Ashita wa ame kamoshirenai.
明日は雨かもしれない。
"It might rain tomorrow."
Kinyoubi desu kara, kondeiru kamoshiremasen.
金曜日ですから、 混んでいるかもしれません。
"Since it is Friday, it might be busy."

The last thing to mention is, darou and deshou can't be used when referring to one's own actions. For example, one would never say, "Ashita watashi wa Kobe ni iku darou" to communicate "I might go to Kobe tomorrow." This would be grammatically incorrect. Kamoshirenai can be used in these situations, instead.

Ashita watashi wa Kobe ni iku kamoshirenai.
明日私は神戸に行くかもしれない。
"I might go to Kobe tomorrow."
Ashita ane wa Kobe ni iku darou.
明日姉は神戸に行くだろう。
"My sister might go to Kobe tomorrow."

Practice Comparing Sentences

Kare wa tabun kin-medaru o toru deshou.
彼はたぶん金メダルを取るでしょう。
"He will probably get the gold medal."
Kare wa kin-medal o totta no kana.
彼は金メダルを取ったのかな。
"I wonder if he got the gold medal."
Kare wa kin-medaru o toru kamoshirenai.
彼は金メダルを取るかもしれない。
"He might get the gold medal."