[shī xiào]
（失去效力） lose efficacy; lose effectiveness; cease to be effective
The medicine no longer has any effect.
這藥已失效了。
（無效） (of a treaty, an agreement, etc.) be no longer in force; become invalid
voidance; voidness of treaties
條約的失效
an invalid cheque
一張失效的支票
automatically cease to be in force
自動失效
This certificate is invalid.
這張證明已失效。