Impedance

How to spell impedance

9 letters · 3 syllables

How to pronounce impedance

Say the part in capitals loudest.

What does impedance mean?

1. nounThe total opposition a circuit presents to an alternating current, combining resistance and reactance.

Impedance in a sentence

• The engineer matched the speaker impedance to the amplifier output.

• A poorly shielded cable can raise the impedance and weaken the signal.

Where does impedance come from?

Language of origin: Latin

Impedance is a relatively modern coinage built on a very old Latin root. It traces back to the Latin verb impedire, meaning 'to hinder' or 'to obstruct', which literally described tangling or shackling someone's feet, from in- 'into' and pes, pedis 'foot'. The same foot-root gives us 'pedal', 'pedestrian' and 'impede', its closest English relative. The abstract noun 'impedance' itself was coined in 1886 by the English physicist and engineer Oliver Heaviside to name the total opposition that an alternating-current circuit offers to the flow of current. It deliberately echoes 'impede', the everyday word for getting in the way, which is the easiest hook for remembering the -ped- in the middle and the -ance ending rather than -ence.

How the word is built

• imped- (from Latin impedire: to hinder, literally to shackle the feet)
• -ance (noun-forming suffix denoting a state or quality)