# compression

/kəmˈpɹɛʃən/ (US) · /kəmpɹˈɛʃən/ (UK)

Source: https://englishreference.com/word/compression
Updated: 2026-06-20

## Senses

### 1. pressing together

noun · CEFR B2

the act of pressing something so it becomes smaller or more solid.

For teachers: the application of pressure to an object or substance to increase its density or reduce its volume.

- The doctor applied a compression bandage to the athlete's swollen ankle.
- The structural integrity of the bridge depends on the concrete's ability to withstand immense compression from the weight of the traffic above.

Usage: Often used in medical contexts like 'compression bandages' or physical contexts like 'soil compression'.

### 2. digital data

noun · CEFR B2

making a computer file smaller so it is easier to store or send.

For teachers: the process of encoding information using fewer bits than the original representation to save storage space or transmission time.

- Without data compression, it would take much longer to download high-quality videos.
- The software uses advanced lossless compression algorithms to ensure that no image detail is sacrificed during the archiving process.

Usage: Commonly used with 'lossy' or 'lossless' to describe the quality of the process.

### 3. audio volume

noun · CEFR C1 · Technical

a way of controlling sound so the loud parts are quieter and the quiet parts are louder.

For teachers: the electronic process of reducing the dynamic range of an audio signal by controlling its gain.

- The producer used compression on the vocals to make them sound more consistent.
- Heavy compression was applied to the drum tracks to give the rock recording a more aggressive and punchy character.

Usage: Usually refers to 'dynamic range compression' in studio recording.

Teaching tip: This is a very specific term in music production; learners might confuse it with file size reduction (MP3) unless the context is clear.

### 4. engine cycle

noun · CEFR C1 · Technical

the part of an engine's movement where the fuel and air are squeezed together.

For teachers: the phase of an internal combustion engine cycle in which the fuel-air mixture is compressed before ignition.

- The mechanic checked the engine because it was losing compression and power.
- A higher compression ratio in the cylinders generally leads to greater thermal efficiency and improved engine performance.

Usage: Often appears in the phrase 'compression stroke' or 'compression ratio'.

### 5. astronomy

noun · CEFR C2 · Technical

when a planet or star is not a perfect circle because it is flattened at the top and bottom.

For teachers: the measure of the deviation of a celestial body from a perfect sphere, typically due to rotation.

- The rapid rotation of Jupiter causes a noticeable compression at its poles.
- Astronomers calculated the polar compression of the planet to better understand its internal fluid dynamics and rotational velocity.

Teaching tip: This is a highly specialised sense; 'flattening' is more common in general scientific discussion.

## Examples

- File compression makes it easier to send large photos by email.
- The engineer explained that the engine works by the rapid compression of air and fuel in the cylinders.
- In digital audio production, dynamic range compression is used to reduce the volume of loud sounds and amplify quiet ones, resulting in a more consistent overall level.

---

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.