In my understanding from this post, 訓練 is a training you do when you start learning something, vs. 練習 which you do to improve continuously. How does 修業 compare to these? I think they're all translated as practice or training, but how is 修業 different than the other two?
(I know this question is similar, but I'll discuss the meaning of 修業 in detail)
練習 is often translated as practice and 訓練 as training. The latter is more formal and systematic.
As for 修業, there are two major meanings, although there is a certain degree of overlap:
- (lifelong) training of (usually oriental) martial arts; (lifelong) religious discipline
- apprenticeship; job training
For the former, imagine what people like Goku (in Dragon Ball) and Dalai Lama do every day. Note that the word is typically written as 修行 in this sense, but even native speakers don't always make strict distinction.
As for the latter, it is very similar to (職業)訓練, but 修行 is usually longer and harder. 修業 tends to be used when traditional-style apprenticeship and long-term self-training is focused. For example, training to be a professional rakugo performer is usually called 修業 rather than 訓練. It may take years to master some skill via 修行, but once you've mastered it, your period of 修業 is over.
I am a native speaker of Japanese but not of English. So my English may not be natural but I hope to be helpful.
修行's definition is following (cited from デジタル大辞泉):
- 悟りをめざして心身浄化を習い修めること。仏道に努めること。 (to train to acquire enlightenment as a Buddhist)
e.g. その仏教徒は悟りに達するために十年間"修行"している (The Buddhist has been training to reach enlightenment for ten years.)
その仏教徒は悟りに達するために十年間"訓練"している or "練習"している sounds a little strange. This is because 訓練 and 練習 are used in more general and practical situations. e.g. 私たちは地震が起きたとき、適切に対処できるように"訓練"している。 (In this case, 修行している is quite strange. 練習している can be an alternative but still 訓練 is more natural.)
- 学問や技芸を磨くため、努力して学ぶこと。 (to practice to polish your skill and acquire knowledge taking much pain)
e.g. 彼は空手を極めるために長年修行している。 (He has been training to be a master of Karate for many years.)
In this case 修行 is similar to 練習, but 修行 is more natural. This is because 修行 is used to reach greater goals than 練習 and 練習 is less great one. e.g. 彼は空手の大会のために練習している。 (He is practicing for the Karate tournament.) In this situation 修行 sounds a bit overstated.
- 「修行」 carries nuance of "polishing", "purification", "making better", "refining"
It most often has religious context and refers to some kind of strict regimen, but not always.
The 練 in「訓練」and「練習」carries the meaning of "training", or "refining" and the other characters provide more specific context...
- 訓 as in 訓読み, carries the meaning of "explanation" ⇒ 「訓練」 (explanation + training)
(sounds like an instructor is teaching how to do something)
- 習 as in 習字, carries the meaning of "practice" ⇒ 「練習」 (training + practice)
(doesn't imply an instructor, could be done alone)