[{"Bold_text": "noun", "List Items": ["a call or summons to engage in any contest, as of skill, strength, etc.", "something that by its nature or character serves as a call to battle, contest, special effort, etc.:Space exploration offers a challenge to humankind.", "a call to fight, as a battle, a duel, etc.", "a demand to explain, justify, etc.:a challenge to the treasurer to itemize expenditures.", "difficulty in a job or undertaking that is stimulating to one engaged in it.", "Military.the demand of a sentry for identification or a countersign.", "Law.a formal objection to the qualifications of a particular juror, to that juror serving, or to the legality of an entire jury.Compare peremptory challenge peremptory challenge.", "the assertion that a vote is invalid or that a voter is not legally qualified.", "Biology.the process of inducing or assessing physiological or immunological activity by exposing an organism to a specific substance.", "Hunting.the crying of a hound on finding a scent."]}, {"Bold_text": "verb (used with object)", "List Items": ["to summon to a contest of skill, strength, etc.Synonyms: invite , bid , dare", "to take exception to; call in question:to challenge the wisdom of a procedure.Synonyms: doubt , impute , question", "to demand as something due or rightful.", "Military.to halt and demand identification or countersign from.", "Law.to take formal exception to (a juror or jury).", "to have a claim to; invite; arouse; stimulate:a matter which challenges attention.", "to assert that (a vote) is invalid.", "to assert that (a voter) is not qualified to vote.", "to expose an organism to a specific substance in order to assess its physiological or immunological activity.", "Archaic.to lay claim to."]}, {"Bold_text": "verb (used without object)", "List Items": ["to make or issue a challenge.", "Hunting.(of hounds) to cry or give tongue on picking up the scent."]}, {"Bold_text": "adjective", "List Items": ["donated or given by a private, corporate, or government benefactor on condition that the recipient raise an additional specified amount from the public:a challenge grant."]}]