das Büro
office
A room or group of rooms where administrative or desk work is done. It is the workplace for many employees.
Ich arbeite von neun bis fünf im Büro.
I work from nine to five in the office.

office / bureau
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office
A room or group of rooms where administrative or desk work is done. It is the workplace for many employees.
Ich arbeite von neun bis fünf im Büro.
I work from nine to five in the office.

For the meaning 'Arbeitsraum' (work space / office), the preposition is important. Movement to this place is expressed with 'ins Büro' (to the office, accusative), while being there requires 'im Büro' (in the office, dative).
Morgens fahre ich mit dem Bus ins Büro.
In the morning, I take the bus to the office.
You can recognize the meaning from the context. If it is about everyday work, the room is usually meant. If 'Büro' (office / bureau) is part of a name like 'Reisebüro' (travel agency) or 'Pressebüro' (press office), an agency is meant.
Mein Schreibtisch steht direkt am Fenster im Büro.
My desk is right by the window in the office.
In connection with the workplace, 'Büro' (office) is often combined with verbs like 'arbeiten' (to work), 'anrufen' (to call), or 'sein' (to be). Fixed expressions like 'ein Büro leiten' (to run an office) or 'ein Büro mieten' (to rent an office) are also common.
Kannst du mich später im Büro anrufen?
Can you call me later at the office?
The meaning of 'Büro' (writing desk) as a piece of furniture is very rare today and is considered outdated. It is found almost only in historical texts or in descriptions of antiques.
Der alte Brief wurde in der Schublade eines antiken Büros gefunden.
The old letter was found in the drawer of an antique writing desk.
office / agency
'Amt' and 'Büro' can both have to do with administration and paperwork, but they are not the same thing. An 'Amt' is a public office or agency, for example a city office where you apply for something. A 'Büro' is usually a room or workplace where people work at a desk. It can also be an organization or department, but it is not automatically a government agency. The words can be confused because in an 'Amt' you often go into a 'Büro'. When you mean the authority or agency itself, you say 'Amt'. When you mean the room or workplace, you say 'Büro'.

Der Lehrer geht ins Büro, um die Unterlagen für den Ausflug zu kopieren.
The teacher goes to the office to copy the documents for the excursion.
Vor der Reise muss Lisa zum Amt, weil sie einen neuen Ausweis braucht.
Before the trip, Lisa has to go to the office because she needs a new ID card.