For the longest time I've been hearing the word ダイヤ and just always assumed it meant "Diamond", but found recently it all means "train schedule". My question is, what word/language did this word originally come from?

2 Answers 2


Original word is from "Diagram" ダイヤグラム, which is a 外来語.


When used in relation to public transportation, ダイヤ means a diagram showing the schedule, or the schedule itself. It is used not only for trains but also for buses, planes, and so on. For example, the schedule of planes can be called as [飛行機]{ひこうき}のダイヤ, [航空便]{こうくうびん}のダイヤ or [空]{そら}のダイヤ.

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    So is "ダイヤ" also used for other kinds of diagrams? Jun 16, 2011 at 0:33
  • @hippietrail: No, I do not think so. As far as I know, ダイヤ for diagram is only used when it refers to public transportation. (As you know, ダイヤ for diamond is unrelated.) Jun 16, 2011 at 0:38
  • @hippietrail: I realized that both Daijirin and Daijisen just say ダイヤ is a shorthand for ダイヤグラム (I ignore diamond here). Since ダイヤグラム can mean diagram in general, I cannot back up what I wrote in my last comment. Hmm. :( Jun 16, 2011 at 2:00

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