hanamaru
Make a polite guess or seek agreement
でしょう adds 'probably' or 'I suppose', a polite guess about something.
JLPTN5
... + でしょう~ deshō
[something] probably / I suppose / right?
It is the conjecture form of the polite copula and goes at the end of the sentence, after a noun, verb, or adjective in plain form. Said with rising intonation it can also softly ask the listener to agree, like 'right?'.
Tips and Common Traps
Hana· Key point
Use でしょう when you're not completely sure — it's a polite way to share a guess without committing to it.
Maru· Common trap
な-adjectives and nouns drop だ before でしょう: 静かでしょう ✓, not 静かだでしょう.