Causative (make someone/something do something) in Japanese is expressed with [verb 未然形 + aux verbs せる/させる]. 五段 verbs and する are followed by せる, and 上一段, 下一段 and 来る are followed by させる.
- 急がせて済みません -> I’m sorry I made you hurry
- あいつに謝らせろ -> Make him apologize
- 社長が皆を集まらせた -> The CEO made us gather. He called a meeting
- そんな事を言ったら彼女を怒らせるだけだ -> You will only make her get angry if you say something like that
- 監督は皆を長時間練習させた -> The manager made everybody practice for long hours
- 店に不良品を替えさせた -> I made the store exchange the defective item
The passive voice “be made to do something” will be [verb +せる/させる+られる]
- 子供の頃親に勉強させられた (勉強する+せる+られる+た) -> I was made to study by my parents, my parents made me study, when I was a kid
- 彼はプロパガンダ映画を見させられた (見る+させる+られる+た) -> He was forced to watch propaganda movies
- チームの成績にはがっかりさせられた (がっかりする+せる+られる+た) -> I was very disappointed by the poor performance of the team
Since [五段 verb+せる+られる] is pretty mouthful, it is often substituted by [五段 verb+される] in conversation:
- 娘に服を買わされた (買わせられた) -> My daughter made me buy her a dress
- 女房の買い物に付き合わされた (付き合わせられた) -> I was forced to accompany my wife for shopping
It might be counter-intuitive, but せる/させる also means “let someone do something”, because whether you make someone or let someone do something, you are the one who is making the decision.
- 彼等は子供にやりたい放題させている -> They are letting their kids do whatever they want
- 彼等は子供を良い学校に行かせている -> They have their daughter go to a very good school
- 彼はもう大人なんだから自由にやらせるべきじゃない？ -> He is already an adult, so shouldn’t you let him do as he wants?
- これは子供には見させられない -> I cannot let children watch this
The archaic forms of せる/させる are す/さす (around the 11-16th centuries), and are often mixed up even today.
- 彼はそれを私に恥をかかすためにやった (In the modern language かかせる) -> He did it to make me look bad
- 好きなようにやらしたら？(やらせたら) -> Why don’t you let him as he wants?
There are very common usages, whether they are technically correct or not.
Also note that there are many verbs that are causative by nature, without せる/させる.
- 彼女は子供に服を着せている (着せる) -> She is dressing her child now
- 彼女は娘に派手な服を着させない (着る+させる+ない) -> She won’t let her daughter wear flashy clothes
- 彼の活躍には驚かされた (驚かす+れる+た) -> I was surprised by his performance
- 酸は鉄を溶かす -> Acid dissolves steel. Acid makes steel dissolve (溶けさせる [溶ける+させる] is correct, but not common)
Also some dictionaries treat some [五段 verb + せる] as an independent word. It is all an academic argument, and it doesn’t make any difference in the practical term.