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REFERENCE

compression

n.
US //kəmˈpɹɛʃən// UK //kəmpɹˈɛʃən// com·pres·sion
  1. 1 pressing together (n.)
    B2 Upper Intermediate

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

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

    Example

    The doctor applied a compression bandage to the athlete's swollen ankle.

    Example

    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. 2 digital data (n.)
    B2 Upper Intermediate Computing

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

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

    Example

    Without data compression, it would take much longer to download high-quality videos.

    Example

    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.
    • decompression
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  1. 3 audio volume (n.)
    C1 Advanced Technical Music

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

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

    Example

    The producer used compression on the vocals to make them sound more consistent.

    Example

    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.

    Teacher's tip

    This is a very specific term in music production; learners might confuse it with file size reduction (MP3) unless the context is clear.
  2. 4 engine cycle (n.)
    C1 Advanced Technical

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

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

    Example

    The mechanic checked the engine because it was losing compression and power.

    Example

    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'.

  3. 5 astronomy (n.)
    C2 Proficiency Technical Science

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

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

    Example

    The rapid rotation of Jupiter causes a noticeable compression at its poles.

    Example

    Astronomers calculated the polar compression of the planet to better understand its internal fluid dynamics and rotational velocity.

    Teacher's tip

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

Borrowed from Middle French compression, from Latin compressiō.

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