Translation guide
A coupler is a device or component that connects two things together. In Japanese, the translation depends on what is being connected: mechanical parts, railway cars, electronic signals, or optical fibers. This guide covers the most common terms for English-speaking learners.
A device that joins two mechanical parts, such as shafts, pipes, or hoses.
The most direct loanword for 'coupler', widely used in mechanical and engineering contexts. Often refers to quick-connect fittings for hoses or pipes.
This coupler is for high-pressure hoses.
A general term for a joint or coupling in piping, plumbing, or mechanical systems. More native-sounding than カプラー.
Please connect the pipes with a coupler.
Specifically refers to a coupler for railway cars or heavy machinery. Not used for small mechanical parts.
The railway car's coupler came off.
A device that transfers electrical signals or power between circuits, often with isolation.
A device that splits or combines light signals in optical fibers.
カプラー is the most versatile loanword and works in most technical contexts. 継手 is a native Japanese term for mechanical joints, often used in piping. 連結器 is specifically for large-scale couplers like those on trains. Use カプラー when unsure.
The air hose coupler broke.
Replace the pipe coupler.
Do not translate 'coupler' as 結合するもの or つなぐもの. These sound unnatural and vague. Use the specific terms above.
The directional coupler distributes power.