1Valid or effective — having force, effect, or usefulness, said of things like contracts, qualifications, or the effectiveness of a measure.
このパスポートはあと三年有効です。
This passport is valid for three more years.
ストレス解消には運動が有効だと言われている。
Exercise is said to be effective for relieving stress.
契約が有効になるのは署名した日からです。
The contract becomes valid from the day it is signed.
そのチケットは平日のみ有効だ。
That ticket is only valid on weekdays.
2A specialized judo term: a score awarded for a technique, historically ranked below 「技あり」(waza-ari); the scoring system has since changed and this score is no longer used in modern competition rules.
審判は投げ技に対して有効を宣告した。
The referee called "yuko" for the throw.