～だろう／でしょう

だろう (plain) and でしょう (polite) mark a sentence as the speaker's conjecture: something they believe is true but do not know directly. The same chip also covers the literary i-adjective form ～かろう.

In English they correspond to “probably”, “I suppose”, or a “will” softened by uncertainty.

1. Making a guess

Put だろう／でしょう after a plain-form sentence to present it as a guess. It often pairs with たぶん (“probably”) or きっと (“surely”).

2. Seeking agreement with rising でしょう？

Said with rising intonation, でしょう？ invites the listener to agree, like English “right?” or “don't you think?”.

3. The weather-forecast でしょう

Japanese weather forecasts end almost every sentence in でしょう. It is the classic polite guess about something no one can know for certain.

How to form it

Plain form + だろう／でしょう. Verbs and i-adjectives keep their plain form. Nouns and na-adjectives attach directly, without だ. The literary ～かろう replaces the final い of an i-adjective.

• 行く（いく）= to go → 行くだろう（いくだろう）= will probably go
• 高い（たかい）= expensive → 高いでしょう（たかいでしょう）= is probably expensive
• 学生だ（がくせいだ）= is a student → 学生だろう（がくせいだろう）= is probably a student
• 静かだ（しずかだ）= is quiet → 静かでしょう（しずかでしょう）= is probably quiet
• 高い（たかい）= expensive → 高かろう（たかかろう）= is probably expensive (literary)

Key idea

だろう／でしょう puts a whole statement under an invisible “probably”. The speaker steps back from the facts and offers their best estimate. With rising intonation, it can instead ask for confirmation or agreement.