die Öffentlichkeit
public
All the people in a society; the general public or audience.
Die Entscheidung der Regierung wurde von der Öffentlichkeit stark kritisiert.
The government's decision was heavily criticized by the public.

public
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public
All the people in a society; the general public or audience.
Die Entscheidung der Regierung wurde von der Öffentlichkeit stark kritisiert.
The government's decision was heavily criticized by the public.

The word is derived from the adjective 'öffentlich' (public). The ending '-keit' turns adjectives into feminine nouns that describe a quality or state — here, the state of being public.
Die Sicherheit der Bevölkerung ist eine öffentliche Aufgabe.
The safety of the population is a public responsibility.
'Öffentlichkeit' (public) is almost always used in the singular and with the definite article 'die'. A plural form practically does not exist.
Die Öffentlichkeit hat ein Recht auf diese Informationen.
The public has a right to this information.
This noun is often used as the object of verbs that describe communication or influence. Typical phrases are 'die Öffentlichkeit informieren' (to inform the public), 'die Öffentlichkeit erreichen' (to reach the public), or 'die Öffentlichkeit täuschen' (to deceive the public).
Mit der Kampagne will die Regierung die breite Öffentlichkeit erreichen.
With the campaign, the government wants to reach the wider public.
The expression 'an die Öffentlichkeit gehen' (to go public) describes the act of making secret information public. The information being revealed is often introduced with the preposition 'mit' (with).
Er entschied sich, mit den Beweisen an die Öffentlichkeit zu gehen.
He decided to go public with the evidence.
The expression 'in der Öffentlichkeit' (in public) describes a place or situation where one can be seen by strangers. It contrasts with 'im Privaten' (in private) or 'zu Hause' (at home).
Bitte streitet euch nicht hier in der Öffentlichkeit.
Please don't argue here in public.
world
'die Welt' and 'die Öffentlichkeit' can both mean people in general. 'die Welt' often sounds very broad and sometimes a bit emotional or informal, especially in expressions like 'die ganze Welt' (the whole world). 'die Öffentlichkeit' is more precise when referring to people as an audience, society, or public opinion. In news, politics, or official texts, 'die Öffentlichkeit' usually fits better. 'die Welt' is more suitable when speaking generally or figuratively about many people.

Die Firma informierte die Öffentlichkeit erst nach der Untersuchung.
The company informed the public only after the investigation.
Nach dem Finale sprach die ganze Welt über dieses Tor.
After the final, the whole world was talking about that goal.