'challenge' as a noun is something that tests one’s abilities or resources, and can be either physical or mental, or both. It can also refer to the act of setting a task or problem to be completed, as well as the reaction to a given task or problem.
1. Learning to play the piano is an interesting challenge.
2. I'm excited for the challenge of compiling a report for the board.
when using 'challenge' as a noun, it is important to remember that 'challenged' cannot be used as a noun. For example, 'The professor liked her challenged' is incorrect; instead, one should say 'The professor liked the challenge she was given.'
as a verb, 'challenge' means to invite or dare someone to engage in a contest, task, or action. It can also mean to question the truth or validity of something or to confront or resist something based on its perceived wrongness or harmfulness.
He challenged me to a game of chess.
The lawyer challenged the evidence presented in court.
The activist challenged the company's unethical practices.
'Challenge' can be used in both transitive (with a direct object) and intransitive (without a direct object) forms. For instance, 'She challenged the decision' (transitive) vs. 'He likes to challenge' (intransitive). The phrase 'rise to the challenge' is an idiomatic expression meaning to show that you can deal with a difficult situation successfully. 'Challenge' can also refer to the act of formally objecting to a potential juror in court. Don't confuse 'challenge' (verb) with 'challenge' (noun). For instance, 'Facing the mountain was a huge challenge' (noun) vs. 'I challenge you to climb that mountain' (verb).