etwa
about / approximately
Used to give an approximate figure; means 'ungefähr' (approximately), 'circa' (about), or 'rund' (around).
Die Reparatur wird etwa 100 Euro kosten.
The repair will cost about 100 euros.

about / approximately
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about / approximately
Used to give an approximate figure; means 'ungefähr' (approximately), 'circa' (about), or 'rund' (around).
Die Reparatur wird etwa 100 Euro kosten.
The repair will cost about 100 euros.

The meaning of 'etwa' changes depending on the type of sentence. In a statement, it means 'ungefähr' (approximately). In a question, however, it often expresses surprise or doubt.
Die Reise dauert etwa zwei Stunden.
The trip takes about two hours.
In the meaning of 'ungefähr' (approximately) or 'circa' (about), 'etwa' always stands directly before the number or quantity it refers to.
Das Gebäude ist etwa 50 Meter hoch.
The building is about 50 meters high.
In a question, 'etwa' is not a neutral particle. It adds an undertone of disbelief, skepticism, or mild reproach to the question.
Hast du etwa gedacht, ich würde das vergessen?
Did you really think I would forget that?
When 'etwa' is used to introduce an example, it has a rather formal and written style. This use is often found in informational texts or presentations.
Einige Säugetiere, etwa Wale und Delfine, leben im Wasser.
Some mammals, for example whales and dolphins, live in the water.
because
'denn' and 'etwa' can both be used in questions, but they give the question a different meaning. 'denn' shows interest, surprise, or sometimes slight impatience, and often makes the question sound more natural in conversation. 'etwa' tends to show doubt or an assumption, often with surprise: you are asking whether something is really the case. Learners may confuse the words because neither carries the main information; instead, both show the speaker's attitude. Remember: 'denn' asks more openly, while 'etwa' sounds more like 'is that really the case?'

Hast du etwa den Schlüssel im Zug vergessen?
Did you really forget the key on the train?
Warum kaufst du denn so viel Brot?
Why are you buying so much bread, then?