Challenge - любят американцы это словечко
и запускают его часто с преувеличением, как на этой картинке.
A challenge is something new and difficult which requires great effort and determination.
I like a big challenge and they don't come much bigger than this...
The new government's first challenge is the economy.
If you challenge ideas or people, you question their truth, value, or authority.
Democratic leaders have challenged the president to sign the bill...
The move was immediately challenged by two of the republics...
I challenged him on the hypocrisy of his political attitudes.
If you challenge someone, you invite them to fight or compete with you in some way.
A mum slashed a neighbour's car tyre and challenged her to a fight after their daughters fell out...
He left a note at the scene of the crime, challenging detectives to catch him...
We challenged a team who called themselves `College Athletes'.
A flaw in something such as a theory or argument is a mistake in it,
which causes it to be less effective or valid.
Almost all of these studies have serious flaws.
A flaw in someone's character is an undesirable quality that they have.
The only flaw in his character seems to be a short temper. = defect, failing
A flaw in something such as a pattern or material is a fault in it that should not be there.
= imperfection