でしょう・
でしょう and だろう present the speaker's current estimate that something is probably true or that an event will probably happen. They are especially natural for predictions based on knowledge, clues, or reasoning.
Predicting an event
天気予報によると、明日は午後から雨が降るでしょう。
According to the weather forecast, it will probably rain tomorrow afternoon.
AnalyzeThe forecast context makes this a prediction, not a request for the listener to agree.
Estimating a present situation
電気がついているから、田中さんはまだ会社にいるだろう。
The lights are on, so Tanaka is probably still at the office.
AnalyzeThe visible clue supports the speaker's estimate about the present.
How the estimate works
The speaker does not claim complete certainty. Instead, the ending marks the statement as the most likely conclusion based on available information. This works well for weather, future results, another person's situation, and other matters that the speaker does not directly control.
Attachment after a na-adjective
大通りから離れているので、この辺りは夜になると静かだろう。
Since this area is away from the main road, it is probably quiet at night.
AnalyzeStart from 静かだ, remove the final だ, and add だろう.
Formal writing
この傾向は今後も続くであろう。
This trend will probably continue.
Analyzeであろう suits reports, essays, and other formal writing.
Three kinds of prediction
でしょう or だろう here presents the speaker's estimate. The same forms can instead seek the listener's agreement, but that is a separate use. かもしれない normally leaves more room for doubt, while はずだ presents something as expected because of a known fact, rule, or plan.
More examples
道が混んでいるので、バスは少し遅れるでしょう。
The roads are crowded, so the bus will probably be a little late.
AnalyzeThe traffic provides the reason for the prediction.
日曜日だから、この店はたぶん休みだろう。
Since it is Sunday, this shop is probably closed.
AnalyzeThis shows direct attachment after a noun.
この時間なら、駅はまだ混んでいないでしょう。
At this hour, the station is probably not crowded yet.
AnalyzeThe negative plain form remains before the ending.
あの雨なら、昨日の試合は中止になっただろう。
With rain like that, yesterday's game was probably canceled.
AnalyzeThe speaker is reasoning about a past result that is not yet known.
準備は十分だから、発表はうまくいくでしょう。
The preparation is thorough, so the presentation will probably go well.
AnalyzeThe amount of preparation supports the prediction.
十年前なら、この建物はまだ図書館ではなかったでしょう。
Ten years ago, this building probably was not a library yet.
AnalyzeA past negative noun form stays intact before でしょう.