1. successful in producing the desired result or effect
2. in operation or in force; actually working or functioning
3. impressive or striking in appearance or effect

Examples

• Regular exercise is an effective way to improve your health.
• The new law becomes effective on January 1st.
• Her speech was effective in convincing the audience to support the cause.
• This medicine is effective against the common cold.
• The company implemented effective strategies to reduce costs.
• The lighting in the theater created an effective atmosphere for the performance.