Dubitative forms are used to express doubt or an assumption. The dubitative is very closely related to the subjunctive in Japanese.

Rentaikei + かな (ka na) or かなあ (ka naa)

This is a simple dubitative. It illustrates a certain amount of doubt you have concerning the statement you just made. かなあ (ka naa) conveys a more significant amount of doubt than かな (ka na).

Sendai ni ikeru ka na.
I wonder if I can go to Sendai.

Nii-chan ga kaimono shimashita ka naa.
I doubt that my brother did the groceries.

だろう(darou) and でしょう (deshou)

Since だ (da) and です (desu) are contractions of である (de aru) and でございます (de gozaimasu), and have the same contractions as ある (aru) and ございます (gozaimasu) have in the subjunctive form.

である de aruであろう de arou
だ daだろう darou
でございます de gozaimasuでございましょう de gozaimashou
です desuでしょう deshou

They should be translated as “it probably is”. だろう (darou) and でしょう (deshou) can be combined with verbal adjectives.

Maiku-kun ga kuru deshou ne.
Mike is coming, right?

Takai darou.
It must be expensive.

Samukatta deshou.
It must have been cold.

The dubitative in the past tense

The ren’youkei + たろう (tarou) is used for the past tense of the subjunctive form. It undergoes contractions when combined with Group 4 (yodan katsuyou) verbs. Please check the ren’youkei + たろう (tarou) page for more details.

Hana ga kattarou.
He’s probably bought the flowers.

It was probably new.

Ame ga furimashitarou.
It has probably rained.

Akakattarou desu.
It was probably red.

The negative subjunctive form

The rentaikei + まい (mai) is the negative form of the subjunctive form. まい (mai) is placed after the main (or closing) verb, also when that closing verb is in the polite form, but cannot be combined with verbal adjectives.

Group 2 verbs are often contracted or abbreviated by removing the final る (ru).

Kono saki wa maa hanashimasumai.
I’d rather not tell you the rest.

Kare wo matsumai.
I don’t think they’ll wait for him. / They probably won’t wait for him.

Are wa dekirumai.
I don’t think that’s possible. / That probably won’t be possible.

Tabemono de wa arumai.
I don’t think that’s food.

Kodomo ja arumai shi, sore gurai wakatteru yo.
I’m quite aware of that, thank you very much. I’m not a child, you know!

Note: When combining まい (mai) with である (de aru), you should insert the particle は (wa) like in ではない (de wa nai), since まい (mai) also is a negative form.

Rentaikei + そう (sou)

The rentaikei + そう (sou) is used to describe “hearsay”. It is only used for information you got from a third party. It is often followed by a form of “de aru” (da / desu).

Ame ga furu sou desu.
I heard it’s going to rain.

Chikatetsu ga takai sou da.
I heard the subway is expensive.

Nihonsei da sou da.
I heard it’s Japanese-made.

Rentaikei + らしい (rashii)

The rentaikei + らしい (rashii) means “to seem” or “to be like”. らしい (rashii) is a verbal adjective and can be conjugated like any other verbal adjective. らしい(rashii) can also be placed directly after nouns. In these cases, it should be translated as “it’s typically” or “it’s just like”.

Ame ga furu rashii.
It appears to be raining.

Kare ga konai rashii desu.
It seems like he’s not coming.

Rentaikei + よう(な) (you na)

The rentaikei + よう(な) (you na) translates as “similar to” or “to seem that”. It is often followed by a form of “de aru” (da / desu). よう (you) can also be written with the kanji 様 (you). When combined with a verb, よう(な) (you na) describes an impression you have.

Ame ga furu you desu.
It appears to be raining.

Atarashii you da.
It seems new.

Ren’youkei + そう(な) (sou na)

The ren’youkei + そう(な) (sou na), often followed by a form of “de aru” (da / desu) is translated as “it looks like”.

Ame ga furisou da.
It looks like it’s going to rain.

Ame ga furisou na ki ga shimasu.
I have the feeling it will rain.

When combining そう(な) (sou na) with a verbal adjective the く (ku) is dropped:

濃く (koku = ren’youkei) → 濃くそう(な) (koku +sou na) → 濃そう(な) (kosou na)

Oishisou da.
It looks tasty.

Kosou na shiru desu.
It’s a thick looking soup.

Two exceptions exist among the verbal adjectives: ない (nai), meaning “there isn’t” and いい (ii), meaning “to be good”. With these two verbal adjectives the く (ku) is replaced with さ (sa):

なく (naku = ren’youkei) → なくそう(な) (naku +sou na) → なさそう(な) (nasasou na)
よく (yoku = ren’youkei) → よくそう(な) (yoku +sou na) → よさそう(な) (yosasou na)

Tanaka-kun ga konasasou da.
It looks like Tanaka won’t be coming.

Yosasou na jisho da.
The dictionary looks like it’s a good one.

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