Learn Hardcore Dutch: Wij hadden de temperatuur gemeten voordat de docent met zijn uitleg begon. - We had measured the temperature before the teacher began his explanation.

In Dutch perfect‐tense constructions the finite auxiliary (here hadden) must occupy the second position, and the past participle (gemeten) goes to the clause’s end. So you get:
Wij (subject) – hadden (auxiliary, 2nd) – de temperatuur gemeten (object + participle at the end).

Why do we use the auxiliary hadden instead of hebben in the first clause?

Hebben is the present‐tense auxiliary, so “we have measured” would be wij hebben gemeten. Here we need past perfect (“we had measured”), so we use the past tense form of hebben, which for wij is hadden.

When should I use the past perfect in Dutch?

Just like in English, you use the past perfect to show that one past action occurred before another past action. In this sentence, measuring the temperature happened before the teacher started explaining, so Dutch uses had(den) + past participle to mark that sequence.

Why is begon at the very end of the subordinate clause introduced by voordat?

Voordat is a subordinating conjunction. In Dutch subordinate clauses the finite verb must go to the end. Inside the clause you keep the normal subject and any prepositional phrases before that final verb:
voordat (subord. conj.) – de docent (subject) – met zijn uitleg (prep. phrase) – begon (verb, final).

Can I start the sentence with voordat instead of placing it in the middle?

Yes. If you front the subordinate clause, you still keep verb‐final there and you should follow it with a comma. For example:
Voordat de docent met zijn uitleg begon, hadden wij de temperatuur gemeten.

What’s the difference between voordat and voor?

Voordat is a conjunction meaning “before” that introduces a subordinate clause.
Voor is a preposition meaning “before” in time or place and must be followed by a noun phrase, not a full clause.
Example:

Conjunction: Voordat hij vertrekt, zet hij zijn fiets op slot.
Preposition: Hij zet zijn fiets op slot voor hij vertrekt.

Why does the teacher beginnen with met zijn uitleg? Couldn’t you say just hij begon zijn uitleg?

Dutch uses the fixed collocation beginnen met + noun when you mean “to start something.” So you say hij begon met zijn uitleg (“he started with his explanation”). Although hij begon zijn uitleg is technically understandable, it’s not the normal pattern.

Why is temperatuur paired with de and not het?

Nouns in Dutch are either de-words or het-words, and temperatuur is a de-word (no simple rule covers all nouns, but many ending in -uur, -ing, -heid, -ie etc. are de). You have to learn each noun’s article, though patterns can help.

In the subordinate clause why is it begon and not begonnen?

Begon is the simple past form of beginnen (“he started”). Begonnen is the past participle, which you would use with an auxiliary (e.g. hij is begonnen – “he has started”). In a subordinate clause that simply sets the time, you use the simple past, so begon.