
der Dienst
duty / shift
The professional activity or work that someone performs at a particular time; working hours or a shift.
Ich habe heute von 8 bis 16 Uhr Dienst.
I'm on duty today from 8 a.m. to 4 p.m.
service / duty
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duty / shift
The professional activity or work that someone performs at a particular time; working hours or a shift.
Ich habe heute von 8 bis 16 Uhr Dienst.
I'm on duty today from 8 a.m. to 4 p.m.

service
A service performed for others, often in exchange for payment.
Viele Firmen bieten mittlerweile einen Lieferservice als zusätzlichen Dienst an.
Many companies now offer a delivery service as an additional service.

to do a favor
To do someone a favor or provide help.
Könntest du mir einen großen Dienst erweisen und meine Blumen gießen, während ich im Urlaub bin?
Could you do me a big favor and water my flowers while I'm on vacation?

service / duty
Work or service in a state organization, especially in the military.
Nach der Schule hat er seinen Dienst bei der Bundeswehr geleistet.
After school, he did his service in the German armed forces.
'Dienst' (service/duty) is the noun related to the verb 'dienen' (to serve). All meanings of 'Dienst' have to do with the basic idea of serving someone or something, or providing a service.
Ein guter Kellner dient seinen Gästen mit Aufmerksamkeit.
A good waiter serves his guests attentively.
When referring to working hours, the collocations 'Dienst haben' (to be on duty), 'im Dienst sein' (to be on duty), and 'außer Dienst sein' (to be off duty) are very common. It is also often used in compounds such as 'Frühdienst' (early shift) or 'Nachtdienst' (night shift).
Die Ärztin hat heute Nachtdienst.
The doctor is on night duty today.
In the sense of a service, 'Dienst' is often found in business contexts. It is at the core of words such as 'Dienstleistung' (service), 'Kundendienst' (customer service), or 'Lieferservice' (delivery service).
Der Reparaturservice dieser Firma ist ausgezeichnet.
This company's repair service is excellent.
The meaning 'favor' occurs almost exclusively in the fixed expression 'jemandem einen Dienst erweisen' (to do someone a favor) or, more colloquially, 'jemandem einen Dienst tun' (to do someone a favor).
Du würdest mir einen großen Dienst erweisen, wenn du mich vom Bahnhof abholst.
You would be doing me a big favor if you picked me up from the station.
You can recognize this meaning from the context of state institutions such as the military ('Bundeswehr'), police, or fire department. The typical verb in this context is 'leisten' (to perform/do).
Er musste nach der Schule seinen Dienst bei der Armee leisten.
After school, he had to do his service in the army.
work
Arbeit and Dienst can both refer to a person’s professional activity. Dienst, however, usually emphasizes a scheduled working period or shift, while Arbeit refers more generally to employment. Use Dienst for a specific schedule and Arbeit when you mean the job as a whole.

Ich habe morgen von acht bis vier Dienst.
I’m on duty from eight to four tomorrow.
Ich gehe morgen zur Arbeit und komme am Nachmittag wieder nach Hause.
I’m going to work tomorrow and will come home again in the afternoon.