制限速度：limit speed? speed limit?

制御部は、制限速度を超えないよう車両の速度を制御する。

ChatGPT:

The control unit controls the vehicle's speed to prevent it from exceeding the speed limit.

あなた:

Why "speed limit" and not "limit speed"?

ChatGPT:

"Speed limit" is the correct and natural phrasing in English because it follows the standard noun-adjective order for set expressions. In this case:

• "Speed limit" → A fixed and widely recognized term that refers to the maximum allowable speed on a road.
• "Limit speed" → This phrasing is unnatural in English and could be misinterpreted. "Limit" is typically a verb or noun, and "limit speed" could sound like an instruction rather than a defined restriction.

In English, compound nouns often follow a "descriptor + main noun" structure, where the main noun (e.g., "limit") is clarified by the preceding word (e.g., "speed"). This is why we say:

• "Speed limit" (not "limit speed")
• "Temperature limit" (not "limit temperature")
• "Weight limit" (not "limit weight")

"Limit speed" might be understood in very specific technical contexts, such as instructions to reduce speed, but it does not mean "the maximum permitted speed."

あなた:

この道路の制限速度は６０キロです。

ChatGPT:

The speed limit on this road is 60 km/h.

あなた:

I understand your explanation of "speed limit", but it may be said that an accurate Japanese translation of "speed limit" is 速度制限 rather than 制限速度. For instance, a Japanese may say この道路には６０キロの速度制限がある。The Japanese 制限速度 means the speed above which the movement of vehicles such as cars is prohibited by law; it is fundamentally a "speed" and not a "limit". In that sense, "limit speed" seems more accurate as the translation of 制限速度 than "speed limit", don't you think?

ChatGPT:

I see your point, and it's a very precise linguistic observation. In Japanese, 制限速度 is indeed a "speed" (速度) that serves as a limit, whereas 速度制限 is a "restriction" (制限) imposed on speed. This distinction aligns with how the two terms function in Japanese grammar and meaning.

However, in English, "speed limit" is the established and idiomatic term for the maximum allowable speed on a road. Even though 制限速度 literally translates to "limit speed," the natural English equivalent remains "speed limit."

That said, if we were to attempt a more literal English rendering of 制限速度 while maintaining its conceptual integrity, "maximum allowed speed" or "restricted speed" might work, though they are not common road sign terminology.

Would you agree that while "limit speed" seems to align better with the Japanese structure, the fixed English expression "speed limit" ultimately prevails due to linguistic convention?

あなた:

I agree. But consider imaginary patent infringement lawsuit situations, such as one where the interpretation of 制限速度 and its translation are at issue. The Japanese patentee may argue that 制限速度 is fundamentally "a speed" and not "a restriction", and hence the English word "speed limit" as its translation was an error, causing confusion and resulting in an ambiguous interpretation of the patentee's invention and therefore the infringement claim hinging on the erroneous interpretation should be rejected, blah blah blah. I don't know the likelihood of such cases but just for the sake of argument, don't you think that's possible and therefore 制限速度 may better be translated as "limit speed" particularly when the text involves patents and other legal documents?

ChatGPT:

Yes, I see where you're going with this, and I think your argument is entirely valid in the context of patents and legal documents, where precise wording can have significant consequences.

If a patent explicitly uses 制限速度, and the fundamental nature of the term as "a speed" (not "a restriction") becomes a point of contention, translating it as "limit speed" might be preferable to maintain a literal and structurally faithful rendering. This would preserve the idea that 制限速度 refers to a particular speed value rather than the act of imposing a restriction.

In everyday English, "limit speed" is uncommon and might seem awkward, but in legal and technical contexts, where absolute precision takes precedence over natural phrasing, it could be justified. If a case were to arise where a patentee argues that the term was mistranslated and led to misinterpretation, a more direct translation like "limit speed" could help avoid ambiguity.

That being said, another possible approach could be "restricted speed" or "maximum permissible speed", which maintain a clearer connection to the idea of a specific speed value while sounding more natural in English.

So, while "speed limit" is standard for general use, I agree that in patents and legal contexts, a case can be made for "limit speed" or an alternative that more explicitly conveys the concept of 制限速度 as a speed itself, not a restriction. Would you lean toward "limit speed" in such contexts, or would you consider something like "restricted speed" to balance accuracy with readability?