bis
until
As a preposition or conjunction indicating an endpoint in time.
Warte bitte, bis ich zurückkomme.
Please wait until I come back.

until / to
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until
As a preposition or conjunction indicating an endpoint in time.
Warte bitte, bis ich zurückkomme.
Please wait until I come back.

When 'bis' is followed by a noun with an article or adjective, you usually need a second preposition such as 'zu' or 'in'. Before place and time expressions without an article, 'bis' often stands alone.
Fahren Sie bitte nur bis zur nächsten Ampel.
Please drive only as far as the next traffic light.
When 'bis' introduces a subordinate clause, it is a conjunction. The conjugated verb then comes at the end of the clause.
Ich warte hier, bis du mit der Arbeit fertig bist.
I'll wait here until you are finished with the work.
In everyday language, 'bis' is used in many short farewell formulas to suggest a future point in time.
Wir sehen uns morgen. Bis dann!
See you tomorrow. Until then!
The combination 'bis zu' (up to) is used to indicate a maximum number or an upper limit. It emphasizes that the stated limit is not exceeded.
In diesem Aufzug dürfen bis zu acht Personen mitfahren.
Up to eight people may ride in this elevator.
The expression 'bis auf' means 'außer' (except) and is almost always used with the accusative.
Der Raum war leer, bis auf einen alten Stuhl in der Ecke.
The room was empty except for an old chair in the corner.
to / too / closed
'zu' and 'bis' can both have to do with a destination in space. 'zu' describes direction toward a destination: you go to a person, a place, or a specific spot. 'bis' emphasizes the endpoint of a route: that is where the movement or area stops. They can be confused because both can answer 'Wohin?' (to where?). The difference is: 'zu' names the destination itself, while 'bis' names the limit or the point up to which you go.

Wir laufen nur bis zur Brücke und drehen dann um.
We only walk as far as the bridge and then turn back.
Sie fährt nach dem Termin zur Apotheke.
After the appointment, she goes to the pharmacy.