This is the 17631st most frequent Polish word.
zgromadzony
"Zgromadzony" means "gathered" or "assembled."
Here 'zgromadzeni' is used as an adjective, derived from the past participle of 'zgromadzić', describing the participants as 'gathered' or 'assembled' in this formal setting.
Zgromadzeni uczestnicy konferencji czekali na rozpoczęcie obrad.
The gathered conference participants were waiting for the meeting to start.
In this sentence, 'zgromadzony' is used as part of a noun phrase, derived from the past participle to describe something that has been amassed or collected, in this case referring to wealth.
Majątek zgromadzony przez całe życie to jego największy skarb.
The wealth accumulated over a lifetime is his greatest treasure.
Here 'zgromadzonych' is a past participle used as a substantive modifier, meaning people who gathered, indicating a group of individuals who have assembled in the hall.