Grammar
들 (보조사)
particle marking multiple participants
Form
Verb connective -고 + auxiliary particle 들 — multiple people perform the action.
Function
The auxiliary particle 들 can follow a connective ending such as -고 and signals that multiple people are the subjects of the action. It differs from the plural suffix -들 attached to nouns.
Why this form?
모두 — “everyone/all” is an independent quantifier; -들 is a plural suffix.
How to build it
Following the connective -고, 들 is an auxiliary particle (e.g., 보고들 있다). It marks a plural subject. This differs from the nominal plural suffix -들 in 사람들.
Forms not to confuse
모두
모두 알고 있어요. — Everyone knows.
Examples
제가 다 들린다는 건 알고들 계시죠? — You all know that I can hear everything, right?
다들 어디 갔어요? — Where did everyone go?