質問: How does 代替する operate? I checked a few dictionaries and most of them list examples like * 路面電車を廃止し、バスで代替する * 代替エネルギー which don't really involve an を. According to the dictionary it's a 他 verb. Am I correct to say that XがYを代替する means X replaces Y? And in a sense it's a 他 verb because X as a subject is doing the action of replacement onto Y (albeit with itself)? > > 一部が破壊されてもすぐに他の部分がその機能を代替する。 > > > 他の部分 replaces その機能 (the broken part)? What prompted me to ask this question was this line: > > 彼らは水や空気 エネルギーの循環を代替し人間が生存可能な環境を提供し続ける都市を築きました。 > > > I don't think I fully understand the relations in this sentence. I feel like I know 彼らは人間が生存可能な環境を提供し続ける都市を築きました, meaning "They built a city that continues to provide an environment possible for humans to exist in", but I don't quite understand how 水や空気 エネルギーの循環を代替し relates to the subject and various objects in the sentence (ie who did the replacing, what was replaced with what).
回答: Yes, XがYを代替する means "X replaces Y". And AがXをYに代替する means "A replace X with [by] X" Though I am not sure of what 彼ら means, 彼らは水や空気 エネルギーの循環を代替し would mean "They replace the circle of water, air and energy with something".