Used for advice and reminders to others. (if you want to... , then you shoud/must do sth.)
Examples:
- 友達をたくさん作りたかったら、自分から積極的に話しかけることだ。If you want to make more friends, you must take the initiative to talk to others.
- 健康的に痩せたかったら、食事の量を控え、適度な運動をすることだ。If you want to lose weight in a healthy way, eat less and exercise moderately.
- 読解力をつけたいのなら、毎日、新聞を読むことだ。If you want to improve your reading comprehension, read the newspaper every day.