unklar
unclear
Not clear or difficult to understand, recognize, or perceive; vague or ambiguous.
Seine Antwort auf meine Frage war sehr unklar.
His answer to my question was very unclear.

unclear
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unclear
Not clear or difficult to understand, recognize, or perceive; vague or ambiguous.
Seine Antwort auf meine Frage war sehr unklar.
His answer to my question was very unclear.

The adjective 'unklar' (unclear) is the opposite of 'klar' (clear). The prefix 'un-' is very productive in German and is often used to reverse the meaning of an adjective or adverb.
Seine Handschrift ist so unklar, dass ich sie nicht lesen kann.
His handwriting is so unclear that I can't read it.
To express uncertainty, the structure 'Es ist unklar, ...' (It is unclear, ...) is often used, followed by a subordinate clause. This subordinate clause, often introduced by 'ob' (whether), 'wer' (who), or 'wann' (when), describes exactly what is uncertain.
Es ist unklar, ob er zur Party kommen wird.
It is unclear whether he will come to the party.
The expression 'sich über etwas unklar sein' (to be unsure about something) describes personal uncertainty. Pay attention to the reflexive structure: the person who is unsure appears with a dative pronoun (mir, dir, sich).
Sie ist sich noch unklar darüber, ob sie den Job annehmen soll.
She is still unsure about whether she should accept the job.
clear
'klar' and 'unklar' form a direct contrast. Something is 'klar' when you understand it well or when there is no doubt. Something is 'unklar' when you do not understand it well, when several interpretations are possible, or when something has not yet been decided. The contrast also works with people: you can be 'sich über etwas klar sein', meaning to understand something or know it for certain. You can be 'sich über etwas unklar sein' when you are unsure or undecided.

Nach dem Gespräch ist meiner Mutter noch unklar, welche Größe sie kaufen soll.
After the conversation, my mother is still unsure which size she should buy.
Nach dem Gespräch ist mir klar, wann der Bus morgen fährt.
After the conversation, it is clear to me when the bus leaves tomorrow.