Effective
な adjective
You know that 効果 means "effect," and 〜的 attaches on to other words to give them a "~al" or "~like" nuance. What does it mean to be "effect-like"? It mean something is effective.
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.
効果的なやり方
effective method
効果的なプレゼン
effective presentation
効果的なインタビュー
effective interview
効果的な学習
effective learning
でも、あなたのチームは効率的だけど効果的ではないよね。
Well, your team is efficient but not effective, don't you think?
ウォーキングが最も効果的なのは、朝だと言われています。
It is said that walking is most effective in the morning.
効果的にやせるには、しっかり寝ることも大切です。
To lose weight effectively, it's also important to get plenty of sleep.