
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.

really / by any chance
Used in a question to express surprise, doubt, or an assumption.
Willst du mir etwa sagen, dass du den Schlüssel verloren hast?
Are you really trying to tell me that you lost the key?

for example
Used to introduce an example; a more formal alternative to 'zum Beispiel' (for example).
Raubtiere, etwa Löwen und Tiger, jagen ihre Beute.
Predators, for example lions and tigers, hunt their prey.
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 give questions a tone of surprise or a particular conversational attitude. Denn is more closely connected to the current situation and asks for an explanation, while etwa expresses a surprised suspicion. Ask about the reason with denn and about a suspected possibility with etwa.

Du wirkst so traurig, hast du etwa die Prüfung vergessen?
You seem so sad. Did you happen to forget the exam?
Du wirkst so traurig, was ist denn passiert?
You seem so sad. What happened?