unpassend
inappropriate
Not suitable or appropriate for a particular situation, occasion, or person.
Seine Jeans und das T-Shirt waren für die Opernpremiere unpassend.
His jeans and T-shirt were inappropriate for the opera premiere.

inappropriate
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inappropriate
Not suitable or appropriate for a particular situation, occasion, or person.
Seine Jeans und das T-Shirt waren für die Opernpremiere unpassend.
His jeans and T-shirt were inappropriate for the opera premiere.

The word is made up of the prefix 'un-' and the adjective 'passend' (suitable/appropriate). 'Passend' means 'geeignet' (suitable) or 'angemessen' (appropriate). 'Unpassend' (inappropriate) is therefore the direct opposite.
Sein lautes Lachen war in der ernsten Situation unpassend.
His loud laughter was inappropriate in the serious situation.
To express what something is inappropriate for, you use the preposition 'für' followed by the accusative. This construction is very common.
Diese Schuhe sind für eine lange Wanderung unpassend.
These shoes are inappropriate for a long hike.
In the meaning 'tactless', 'unpassend' (inappropriate) is often combined with words that describe communication. Typical examples are: 'eine unpassende Bemerkung' (an inappropriate comment), 'ein unpassender Witz' (an inappropriate joke), or 'eine unpassende Frage' (an inappropriate question).
Er ist bekannt dafür, im falschen Moment unpassende Witze zu machen.
He is known for making inappropriate jokes at the wrong moment.
correct / right
'richtig' and 'unpassend' form an opposite pair when the question is whether something fits a situation. 'richtig' then means suitable or appropriate for the purpose. 'unpassend' means not suitable for the occasion, the person, or the moment. 'unpassend' is especially natural with clothing, behavior, words, or jokes. A comment, for example, can be factually true but still 'unpassend' if the timing is bad.

Nach der schlechten Nachricht fand ich den Witz unpassend.
After the bad news, I found the joke inappropriate.
Vor dem Arzttermin war es richtig, alle Medikamente aufzuschreiben.
Before the doctor's appointment, it was right to write down all the medications.