coupling

noun

• 1a device for connecting parts of machinery: undo the couplings so you can lift the pump out
• a fitting on the end of a railway vehicle for connecting it to another: a train with couplings of the continental pattern

• 2 [mass noun] the pairing of two items:the coupling of tribunals with ministerial enquiries
• an interaction between two electrical components by electromagnetic induction, electrostatic charge, or optical link: mutually inductive coupling

• 3 [mass noun] the action of mating or having sexual intercourse.

• 4two people in a romantic relationship; a couple.