an appeal (=the action of asking a higher court to review and change the decision of a lower court)
He said the campaign would lodge a challenge with the Constitutional Court.
the action of not accepting someone or something's authority; the action of trying to replace someone or something in a position of authority
The issue of a leadership challenge made an immediate return to the top of the political agenda.
the action of questioning whether something is legal, correct, accurate, or true etc
It represented a challenge to these commonly held beliefs.