Effectiveness
In Effect, Efficacy
noun
Something's effective power is its effectiveness. If it has effective power, it remains in effect.
This word usually refers to the legal force or effectiveness of a law, agreement, contract, or treaty, but it can also be used to talk about the efficacy of other things, such as medicine.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
その条約は明日で効力を失う。
That treaty will cease to be in effect from tomorrow.
あなたの今日のプレゼンテーションは、前回に比べて効力が少し弱いような気がしました。
Your presentation today seemed like it was a bit weaker in its effectiveness compared to the last one.
この薬を飲むと、あなたは空を飛べるようになります。でも、飛んでいる時に薬の効力が切れると大変なので、気をつけてくださいね。
If you take this medicine, you will be able to fly in the sky. However, please be careful because if the effect of the medicine wears off while you are flying, it could be very dangerous.
調停が成立したときに作成される調停調書は、判決と同様の効力を有します。
When a mediation agreement is reached, the mediation report created thereafter holds the same legal effect as a court judgment.