When you didn't want to, but you had to
Causative-passive 〜させられる says 'I was made to do ~' — combining the causative ('make ~ do') with the passive ('be ~ed by'). It always carries the nuance that the speaker was forced or obligated against their preference. Form: take the causative form, then make it passive. 食べる → causative 食べさせる → passive 食べさせられる ('be made to eat'). For う-verbs, the long form 〜させられる usually shortens to 〜される: 待たせられる → 待たされる, 書かせられる → 書かされる. Caution: this short form looks identical to the regular passive of う-verbs that already end in 〜す (話す → 話される is just plain passive, never shortens further), so す-ending verbs keep the long causative-passive 話させられる.
How to build it — long form
Causative-passive = causative + passive. る-verbs: 食べる → 食べさせる → 食べさせられる. 見る → 見させる → 見させられる. う-verbs (long form): 書く → 書かせる → 書かせられる. 読む → 読ませる → 読ませられる. 持つ → 持たせる → 持たせられる. 行く → 行かせる → 行かせられる. Irregulars: する → させる → させられる. 来る → 来させる → 来させられる (read こさせられる). The whole thing is a る-verb: 食べさせられる → 食べさせられます, 食べさせられた, 食べさせられて.
The う-verb shortcut: 〜される
In speech, う-verb causative-passives are almost always shortened by collapsing 〜せられる → 〜される. 待たせられる → 待たされる ('be made to wait'). 書かせられる → 書かされる ('be made to write'). 飲ませられる → 飲まされる ('be made to drink'). 行かせられる → 行かされる ('be made to go'). The shortcut sounds more natural; the long form is technically correct but stiffer. Important exception: う-verbs ending in 〜す (話す, おす, かす) don't shorten, because the result would collide with the regular passive. 話す → 話させられる stays as 話させられる (no 〜される version).
The 'I really didn't want to' nuance
〜させられる is the go-to form for venting about coercion: doing chores, being put on the spot, made to drink at a work party, made to wait for a long time. きのう、ぶちょう に お酒 を たくさん 飲まされました。 = 'Yesterday I was made to drink a lot of alcohol by my boss.' 三時間 も 待たされました。 = 'I was made to wait for three whole hours.' 子ども の とき、毎日 ピアノ を れんしゅう させられました。 = 'When I was a kid, I was made to practice piano every day.' If there's no coercion (you wanted to do it), use plain past tense, not 〜させられる.
Causative-passive vs. plain passive — who's the agent
Plain passive: しかられた ('I was scolded') — somebody acted ON me. Causative-passive: 食べさせられた ('I was made to eat') — somebody forced ME to act. The agent (the one doing the forcing) is marked with に: 母 に やさい を 食べさせられました。 = 'I was made by my mother to eat vegetables.' 先生 に 立たされました。 = 'I was made to stand (as punishment) by the teacher.' The forced person is the subject; the forcer is に.
Subtle: 'made to feel'
〜させられる isn't only for physical forcing — it also covers being made to feel something by a situation or experience: この えいが を 見て、いろいろ かんがえさせられました。 = 'Watching this movie made me think about a lot of things.' その 本 に かんどう させられました。 = 'I was deeply moved by that book (literally: made-to-be-moved by that book).' Here the 'agent' isn't a person — it's the experience itself. This is a slightly literary use, very common in essays and reviews.
Quick recognition table — 待つ as the example
待つ (wait, う-verb): plain 待つ → polite 待ちます → potential 待てる → passive 待たれる ('be waited for') → causative 待たせる ('make ~ wait') → causative-passive long 待たせられる → causative-passive short 待たされる ('be made to wait'). The shortest form 待たされる is what you'll actually hear. Drill the core verbs in this pattern: 書く → 書かされる, 飲む → 飲まされる, 歌う → 歌わされる (う→わ), 行く → 行かされる, 読む → 読まされる.
