Pillow Glossary — A to Z of Pillow and Sleep Terms Explained

Confused by pillow jargon? Here is every term you need to know when buying an ergonomic pillow, explained clearly by pillow reviewer Sarah Mitchell.

Last reviewed: October 2026

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Cervical Pillow: A pillow designed to support the natural curve of the cervical spine (the neck). Usually contoured or shaped differently to a standard flat pillow. Also known as an orthopaedic pillow or contour pillow.
Cervical Spine: The seven vertebrae at the top of the spine, running from the base of the skull to the upper back. Correct support of the cervical spine during sleep is the primary function of an ergonomic pillow.
CertiPUR-US: An independent programme for foam products confirming they are made without certain harmful chemicals and have low VOC emissions. Check the manufacturer's listing to confirm whether a specific pillow's foam carries it.
Contour Pillow: A pillow with an uneven profile — typically a raised outer edge and a lower central cradle — designed to maintain the neck in a neutral alignment. The Derila Ergo is a contour pillow.

Down Pillow: A pillow filled with the soft feathers from duck or goose. Very soft and luxurious but provides less neck support than memory foam. Not recommended for neck pain.

Ergonomic Pillow: Any pillow designed to reduce physical strain during sleep by supporting the body's natural alignment. In practice, this typically means a pillow designed to maintain the cervical spine in a neutral position.

Hypoallergenic: A product designed to minimise the risk of allergic reactions. Both Cloudpillo and Derila Ergo use hypoallergenic covers and fill.

Loft: The height of a pillow. Side sleepers generally need a higher loft than back sleepers, and stomach sleepers need the lowest loft of all. Adjustable pillows like Cloudpillo allow you to change the loft to suit your sleep position.

Memory Foam: A viscoelastic foam material that conforms to body heat and pressure, then returns to its original shape when the pressure is removed. Used in both Cloudpillo (shredded) and Derila Ergo (solid contour).

Off-Gassing: The smell that some new foam products emit for the first 24-48 hours after unboxing. Caused by volatile organic compounds in the foam. Generally harmless but can be noticeable. Owners report a mild initial smell with Cloudpillo and little to none with Derila Ergo.
Orthopaedic Pillow: A pillow specifically designed to support correct alignment of the spine and joints during sleep. Functionally equivalent to a cervical or ergonomic pillow.

Phase-Change Material: A material that absorbs and releases heat to regulate temperature. Used in the Cloudpillo Recharge cover to improve cooling performance.
Pillow Loft: See Loft.

Shredded Memory Foam: Memory foam that has been shredded into small pieces to create an adjustable, malleable fill. Used in Cloudpillo. More breathable than solid memory foam and allows loft adjustment by removing or adding fill.
Side Sleeper: Someone who primarily sleeps on their side. Side sleepers need a higher pillow loft than back sleepers to fill the shoulder-to-neck gap and maintain neutral spinal alignment. See our best pillows for side sleepers.
Sleep Position: The position in which you sleep — side, back, or stomach. Your sleep position is the single most important factor in determining which pillow is right for you.
Spinal Alignment: The positioning of the spine in a neutral, anatomically correct posture. An aligned spine during sleep reduces muscle tension and can help minimise neck and back pain.

TENCEL: A soft, breathable fabric made from sustainably sourced wood pulp. Used for some pillow covers. Naturally moisture-wicking and gentle on skin.
Trial Period: The period during which you can return a pillow for a refund. Cloudpillo offers 100 nights. Derila Ergo offers a 60-day money-back guarantee. Always buy from a brand with at least a 30-night trial.

Visco-Elastic Foam: The technical term for memory foam. A polymer foam that responds to both temperature and pressure, allowing it to conform to the body.

Put the terms to work with our head-to-head comparison and buying guides.