
einweihen
to inaugurate
To officially put a new building, facility, or monument into use with a formal ceremony.
Nächste Woche wird die neue U-Bahn-Linie feierlich eingeweiht.
Next week, the new subway line will be ceremoniously inaugurated.
to inaugurate / initiate
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to inaugurate
To officially put a new building, facility, or monument into use with a formal ceremony.
Nächste Woche wird die neue U-Bahn-Linie feierlich eingeweiht.
Next week, the new subway line will be ceremoniously inaugurated.

to let someone in on something
To entrust a person with a secret, a plan, or confidential information.
Er war der Einzige, den sie in ihre Pläne eingeweiht hatte.
He was the only one she had let in on her plans.

to christen
To use something for the first time, often in a special or celebratory way.
Wir haben die neue Terrasse am Wochenende mit einer Grillparty eingeweiht.
We christened the new terrace with a barbecue party over the weekend.
'Einweihen' (to inaugurate / initiate) is a separable verb. The prefix 'ein-' goes at the end in a main clause. In a subordinate clause, the verb stays together, and in the infinitive with 'zu', 'zu' goes in the middle.
Der Bürgermeister weiht die neue Schule ein.
The mayor inaugurates the new school.
The verb comes from 'weihen', which means 'to consecrate' or 'to dedicate' and has a ceremonial character. So 'einweihen' literally means to dedicate something to its purpose through a first, special action.
Lasst uns die neue Kaffeemaschine feierlich einweihen!
Let's ceremoniously christen the new coffee machine!
When informing someone about a secret, the fixed structure 'jemanden (accusative) in etwas (accusative) einweihen' is used. The preposition 'in' is crucial here.
Ich muss dich in meinen geheimen Plan einweihen.
I have to let you in on my secret plan.
In the meaning of 'offiziell eröffnen' (to officially open), 'einweihen' (to inaugurate) is typically used for public structures such as 'ein Gebäude' (a building), 'eine Brücke' (a bridge), 'ein Museum' (a museum), or 'ein Denkmal' (a monument).
Der neue Park wurde am Samstag vom Bürgermeister eingeweiht.
The new park was inaugurated by the mayor on Saturday.
to open
A new building can be described as being „eröffnet“ or „eingeweiht“. Eröffnen emphasizes that it becomes accessible to the public and that its use begins; einweihen places more emphasis on the official, often ceremonial handover. When the focus is on the start of operations, eröffnen is more appropriate; for a ceremony, einweihen is more appropriate.

Die Stadt weiht das neue Kulturzentrum am Samstag mit einer Feier ein.
The city is inaugurating the new cultural center with a ceremony on Saturday.
Die Stadt eröffnet das neue Kulturzentrum am Montag für alle Besucher.
The city is opening the new cultural center to all visitors on Monday.