Translation guide
How to express that something works, produces results, or is in effect in Japanese.
Say that a method, medicine, or action works or is successful.
Common verb for medicine, treatment, or measures taking effect. Often used for things that 'work' on a problem.
この薬はよく効く。
This medicine is very effective.
That method didn't work at all.
Literally 'has an effect'. Neutral and widely used for anything from medicine to policies.
This exercise is effective for dieting.
Means 'valid' or 'effective'. Often used for measures, strategies, or official things. Slightly formal.
This measure is effective.
Similar to 効果がある but more colloquial. Often used for medicine or immediate results.
This medicine takes effect quickly.
Say that a law, rule, or agreement is currently valid or applicable.
Used for tickets, contracts, laws, etc. that are valid or in effect.
This ticket is effective until tomorrow.
That law is still in effect.
Literally 'has legal force'. Used for contracts, laws, or official documents.
This contract is still effective.
Can sometimes be used for rules or threats, but mainly for physical effects. Use with caution.
Not the primary choice for legal validity; 有効 is safer.
Say that a tool, machine, or system works properly.
効く is a casual verb often used for medicine or immediate effects. 効果がある is a general phrase meaning 'has an effect', suitable for most situations. 有効 is more formal and often used for validity of tickets, laws, or strategies.
The medicine works.
Exercise is effective for health.
This password is valid.
That threat isn't effective on him.
This app is really effective.