
die Verwechslung
mix-up
A mistake in which a person or thing is wrongly taken for another.
Entschuldigen Sie, das war eine Verwechslung, ich dachte, Sie wären Herr Meier.
Excuse me, that was a mix-up; I thought you were Mr. Meier.
mix-up
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mix-up
A mistake in which a person or thing is wrongly taken for another.
Entschuldigen Sie, das war eine Verwechslung, ich dachte, Sie wären Herr Meier.
Excuse me, that was a mix-up; I thought you were Mr. Meier.

confusingly similar
A fixed expression that indicates that two people or things are so similar that they can easily be confused with each other.
Die beiden Zwillingsschwestern sehen sich zum Verwechseln ähnlich.
The two twin sisters look confusingly similar.
'Verwechslung' (mix-up) comes from the verb 'verwechseln' (to confuse / mix up). The prefix 'ver-' here indicates an error or misunderstanding, and 'wechseln' (to change / exchange) describes the exchange. The ending '-ung' forms the noun for this process.
Durch eine Verwechslung der Namen erhielt die falsche Person den Preis.
Because of a mix-up of the names, the wrong person received the prize.
If you want to say what was confused with what, you use the structure 'Verwechslung von A mit B' (confusion of A with B). Here, 'A' stands for the person or thing in front of you, and 'B' for the one you think it is.
Die Verwechslung von Salz mit Zucker hat den Kuchen ungenießbar gemacht.
The mix-up of salt with sugar made the cake inedible.
The expression 'zum Verwechseln ähnlich' (confusingly similar) is a fixed expression. It is used to describe an extreme similarity and usually comes directly after the adjective 'ähnlich' (similar).
Diese Kopie ist dem Original zum Verwechseln ähnlich.
This copy is confusingly similar to the original.
error / misconception
Irrtum generally refers to an incorrect assumption. Verwechslung is a particular kind of Irrtum in which one specific person or thing is mistaken for another. Use “Irrtum” for an incorrect assessment without this kind of substitution; when two specific things or people are mistaken for each other, “Verwechslung” is more precise.

Die Verwechslung entstand, weil ich den neuen Lehrer für den Hausmeister hielt.
The mix-up happened because I took the new teacher for the janitor.
Mein Irrtum war, dass ich den neuen Lehrer für den Hausmeister hielt.
My mistake was that I took the new teacher for the janitor.