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.
このカプラーは高圧ホース用です。
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.
パイプを継手で接続してください。
Please connect the pipes with a coupler.
Specifically refers to a coupler for railway cars or heavy machinery. Not used for small mechanical parts.
鉄道車両の連結器が外れた。
The railway car's coupler came off.
A device that transfers electrical signals or power between circuits, often with isolation.
Used in electronics for devices like optocouplers or directional couplers. Often part of compound terms.
フォトカプラーは信号を絶縁します。
The photocoupler isolates the signal.
A more formal term for a coupler in RF or microwave engineering, such as a directional coupler.
方向性結合器は電力を分配します。
The directional coupler distributes power.
A device that splits or combines light signals in optical fibers.
The standard term for an optical fiber coupler. Often used in telecommunications.
光カプラーで信号を分岐します。
We split the signal with an optical coupler.
A more formal alternative, often seen in technical documentation.
この光結合器は低損失です。
This optical coupler has low loss.
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.
エアホースのカプラーが壊れた。
The air hose coupler broke.
配管の継手を交換する。
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.