The expressions used to form an opinion or supposition about (something) on the basis of incomplete information – conjectures are really numerous and commonly used in Japanese and are really problematic for language learners. In this post, I will explain you nuances they have. Believe it or not, but once you know them, they become much easier to understand and use.
ようだ has the highest degree of certainty, it is based on reliable, firsthand information and is used to express likelihood or similarity. みたい is equal to ようだ, however, it is a more casual expression. If the sentence is counterfactual (something seems to be A, but in reality is not) まるで (just) can be added.
たけしの 車は 高いようだ。
たけしの車は高いようだ。(the speaker knows the exact price, so based on the reliable information he infers it is high.)
Takeshi’s car is expensive.
She seems to be Loyd and Yor’s daughter.
そうだ is used with adjectives to indicate similarity or conjecture based on direct visual evidence. This is the usual way to say that something looks delicious (because it looks tasty).
This use of そう follows the stem of verbs and adjectives! （降る→降り、高い→高、大丈夫だ→大丈夫 and so on)
武の 車は 高そうだ。
Takeshi’s car is expensive. (the speaker sees the car, and based on how well it looks he/she guesses that it is expensive)
When そうだ follows a verb, it often indicates that there is a probability of something happening very soon, based on the visual evidence. For example, the weather is about to change (it got dark, all of a sudden)
この 家は 崩れ落ちそうだぞ。
This house is about to fall down!
今日は 雨が 降りそうだ。
It seems it will rain today.
Another use of そう is to indicate hearsay, however, this follows the dictionary form of verbs and い adjectives. And the だ in the case of nouns and なadjectives.
I heard it will rain today. (In the case of the conjecture, stem form 降り is used)
By the way, そうにみえる、ようにみえる are often used to emphasize that some judgment has been made based on visual cues. It is often used to express that something visually seems to be A, but in reality, it is not so.
武は 健康そうに 見えるけど
Takeshi looks healthy, but (in reality, he is sickly or something like that)
らしい indicates that something is inferred from indirect, second-hand evidence, for example, what we have read, been told, and so on.
たけしの 車は 高いらしい。
Takeshi’s car seems to be expensive. (Based on what the speaker heard from friends, for example, he/she infers that the car is expensive)
車で 移動すると 約 3 時間かかるらしい。
I heard it takes about 3 hours if you drive by car.
Another use of らしい is to indicate that someone/something meets the standards of being A or expresses the typical traits of A. When the same noun is repeated (AらしいA), it expresses a perfect example, apex, real. Like: ‘manly man’, etc.
トモちゃんは 女の子だけど、 女らしくない。
Tomo-chan is a girl, but she is unladylike.
Behave like an adult!
に違いない is used when the speaker is sure that there is no mistake in his guessing.
彼らはともこさんから 何か 望むに 違いない。
Without a doubt, they must want something from Tomoko.
Without a doubt, he must be there!
でしょう(だろう) then it is just a conjecture/guess, without outside information, based on some reasoning. Something like a thought experiment. So the certainty is lower than the expressions mentioned above. でしょう is more polite than だろう。
I guess Takeshi’s car is expensive. (the speaker just guesses that it’s expensive)
I guess, he is free on Sundays.
Another use of だろう/でしょう is asking for the hearer’s agreement. Similar to sentence-final particle ね. However, in this use だろう・でしょう are said with rising intonation.
Mary and Takeshi are friends, right?
かもしれない indicates probability (and information is not really based on any evidence, but rather reasoning) even lower than だろう・でしょう. It is similar to English might. It can be used with もしかしたら・もしかすると・もしかして for emphasis.
I think this might be a murder scene!
小さな 振動で 爆発するかもしれない!
The slightest vibration might set it off!
I am mrnoone, and this was briefjapanese.