[wú xiào]
of no avail; to no avail; invalid; null and void; nullity （合同等的）; in vain; unavailability; ineffectiveness; inefficiency; futility; flop
nullify an election
宣布選舉無效
fail to respond to medical treatment
醫治無效
declare decision invalid
宣布決定無效
an invalid contract
無效的契約
make the investment inefficient
無效投資