# impedance

/ˌɪmˈpidəns/ (US) · /ɪmpˈiːdəns/ (UK)

Source: https://englishreference.com/word/impedance
Updated: 2026-08-27

## Senses

### 1. electricity

noun · CEFR C2 · Technical

the total resistance that a circuit gives to an alternating current.

For teachers: the total effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance.

- The speakers have an impedance of eight ohms, so they work well with this amplifier.
- Matching the output impedance of the amplifier to the input impedance of the loudspeakers is critical for efficient power transfer and signal integrity.

Usage: Usually uncountable when referring to the physical property, but countable when referring to a specific value measured in ohms.

### 2. physics and acoustics

noun · CEFR C2 · Technical

the way a material or system resists the flow of energy, like sound waves.

For teachers: a measure of the opposition that a system presents to the flow of energy from a source, such as acoustic or mechanical waves.

- The doctor checked the impedance of the patient's ear to see if there was fluid inside.
- Acoustic impedance is a fundamental property that determines how much sound energy is reflected or transmitted at the boundary between two different media.

### 3. a hindrance

noun · CEFR C2 · Formal

something that stops or slows down progress.

For teachers: the act of impeding or a physical or metaphorical hindrance that obstructs progress.

- The lack of funding was a major impedance to the research project.
- Bureaucratic impedance often prevents small businesses from accessing the grants they need to scale their operations effectively.

Teaching tip: In non-technical contexts, 'impediment' or 'obstacle' is much more common; 'impedance' is usually reserved for scientific discussions.

## Examples

- The speakers have an impedance of eight ohms.
- Engineers must match the impedance of the transmitter to the antenna to ensure maximum power transfer and signal clarity.
- In high-fidelity audio engineering, maintaining consistent impedance across all components is vital to prevent signal degradation and ensure the accurate reproduction of complex acoustic waveforms.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.