Learn Hardcore German: Meine Freundin sagt unsere Verabredung ab, weil sie heute viel Wichtiges im Büro erledigen muss. - My girlfriend cancels our date because she has to do many important things at the office today.

In a main clause in the present tense, the conjugated part (sagt) must be in second position, and the prefix (ab) goes to the end of the clause:
- Meine Freundin sagt unsere Verabredung ab.
If you put it into a form where the verb goes to the end (e.g. an infinitive construction or a subordinate clause with a modal), it stays together:
- … weil sie unsere Verabredung absagen muss.

So: main clause → sagt … ab, verb-final structure → absagen together.

Why does weil sie heute viel Wichtiges im Büro erledigen muss have the verb at the end?

Weil introduces a subordinate clause (Nebensatz). In standard German, subordinate clauses have the finite (conjugated) verb at the end.

Main clause: Meine Freundin sagt unsere Verabredung ab
→ verb in 2nd position (sagt)
Subordinate clause with weil: weil sie heute viel Wichtiges im Büro erledigen muss
→ verb group at the end (erledigen muss)

So: weil → the clause that follows must have verb-final word order in correct written German.

Why are there two verbs at the end: erledigen muss? Which one is the “real” verb?

You have a modal verb plus a main verb:

muss = modal verb (müssen, “must / have to”)
erledigen = main verb (“to get done / to take care of / to deal with”)

In a subordinate clause with a modal:

The main verb is in the infinitive and comes before the modal.
The modal verb (conjugated) is last.

So we get: … weil sie … erledigen muss.

In a main clause with a modal, it looks like this:

Sie muss heute viel Wichtiges im Büro erledigen.
(modal in 2nd position, main verb at the end)

Why is Wichtiges capitalized, and what kind of word is that?

Wichtiges here is a nominalized adjective – an adjective used as a noun.

The base adjective is wichtig (“important”).
When you use it without an actual noun, it becomes a noun in meaning and is written with a capital letter:
- viel Wichtiges ≈ “a lot of important things / a lot of important stuff”

Grammatically:

viel Wichtiges is the direct object of erledigen (accusative).
viel is an indefinite quantifier.
Wichtiges is treated as a neuter singular noun (something like “important stuff”), therefore it gets the ending -es in accusative after viel.

So viel Wichtiges literally means “much important [thing/stuff]”, understood as “a lot of important work/things”.

What is the difference between viel Wichtiges and viele wichtige Dinge?

Both are possible, but the nuance is slightly different:

viel Wichtiges
- grammatically: neuter singular, more like a mass of work/important stuff
- sounds a bit more compact and idiomatic: “a lot of important work / a lot of important stuff”
viele wichtige Dinge
- grammatically: plural, countable things
- emphasizes individual items more: “many important things”

In this sentence, viel Wichtiges fits very naturally, because “important stuff to do at the office” is often thought of as a general mass of work.

Why is it unsere Verabredung, not unser Verabredung?

Verabredung is feminine (die Verabredung).

Possessive determiners like mein, dein, sein, unser take endings similar to the indefinite article ein:

Feminine singular, nominative and accusative: meine, deine, seine, unsere …

In this sentence, unsere Verabredung is in the accusative (direct object of absagen), feminine singular:

unsere Verabredung = “our date / our meeting”

So for feminine Verabredung, you must use unsere, not unser.

What exactly does Verabredung mean here, and how is it different from Termin?

Verabredung usually refers to an informal arrangement between people, such as:

meeting with friends
a date
going out for coffee, dinner, etc.

Examples:

Wir haben eine Verabredung im Café. – “We have a date/meeting at the café.”

Termin is more formal / official, often for:

doctor’s appointments
business meetings
administrative appointments

Examples:

Ich habe morgen einen Termin beim Arzt. – “I have a doctor’s appointment tomorrow.”

In your sentence, Verabredung suggests a more personal or social plan, not a formal appointment.

Does meine Freundin mean “my friend” or “my girlfriend”?

It can mean either, depending on context:

Literally, Freundin is just the female form of Freund (“friend”).
But meine Freundin is very often understood as “my girlfriend” (romantic partner), especially if no other context is given.
If you want to make clear it is just a (female) friend, people sometimes say:
- eine Freundin von mir – “a (female) friend of mine”

So in isolation, many native speakers will first understand meine Freundin as “my girlfriend”, but context can shift it back to “my (female) friend”.

Why is it im Büro and what case is that?

Im is a contraction of in dem:

in
- dem (dative, neuter singular for das Büro) → im

The preposition in takes:

dative for location (where?)
→ im Büro = “in the office”
accusative for direction/movement (where to?)
→ ins Büro (in + das) = “into the office”

In your sentence, she already is at the office doing things there, so we talk about a location, which requires dative: im Büro.

Could we say ins Büro instead of im Büro here?

No, not with the same meaning.

im Büro (in + dem, dative) = location: “in the office”
ins Büro (in + das, accusative) = direction: “into the office” / “to the office”

Your sentence is about things she has to do at the office, not about her going to the office, so im Büro (location, dative) is correct.

Why is heute placed before viel Wichtiges im Büro? Is there a rule for this word order?

German has some general tendencies for adverbial order, often summarized as:

Time – Manner – Place (TMP)

In your clause:

heute = time
im Büro = place
viel Wichtiges = direct object, which commonly appears before adverbials of place

So … weil sie heute viel Wichtiges im Büro erledigen muss follows a natural pattern:

subject: sie
time: heute
object: viel Wichtiges
place: im Büro
verb group: erledigen muss

Other orders are possible, but this one sounds very neutral and idiomatic.

Does there always have to be a comma before weil?

Yes, in standard German weil introduces a subordinate clause, and subordinate clauses are separated by a comma.

Meine Freundin sagt unsere Verabredung ab, weil sie heute viel Wichtiges im Büro erledigen muss.

So you must write the comma before weil in correct written German.

(Spoken German sometimes uses weil with main-clause word order, but the comma is still there in writing.)

What is the difference between weil and denn here?

Both can express a reason, but they behave differently:

weil:
- introduces a subordinate clause
- verb goes to the end of that clause:
  - …, weil sie heute viel Wichtiges im Büro erledigen muss.
denn:
- is a coordinating conjunction (like und, aber)
- the following clause keeps normal main-clause word order (verb in 2nd position):
  - Meine Freundin sagt unsere Verabredung ab, denn sie muss heute viel Wichtiges im Büro erledigen.

Both are correct, but weil feels slightly more causal in everyday speech; denn is a bit more formal or written.

What tense is the sentence in, and why is present tense used for something happening “today”?

The sentence is in the present tense (Präsens):

sagt (from sagen)
muss (from müssen)

German often uses the present tense to talk about:

things happening right now
things happening later today / in the near future

The word heute (“today”) makes it clear that the action is about today, so you don’t need a separate future tense form. German has Futur I, but for everyday speech, present + time expression is much more common:

Sie muss heute viel Wichtiges im Büro erledigen.
= “She has to get a lot of important things done at the office today.” (future meaning from context)