A pillow specifically supports your head while you lie down, usually on a bed. A cushion is the broader word for a soft pad used for comfort when sitting or leaning, such as on a sofa or chair. A simple memory hook: your head rests on a pillow, your body leans on a cushion.
The core difference
Pillow is for the head in bed, cushion is for sitting or leaning, and cushion also has extra figurative uses pillow does not.
- pillow — a soft cushion used to support the head while lying down: He fluffed his pillow before settling in for the night.
- cushion — a soft fabric pad used for comfort when sitting or leaning: She fluffed up the cushions on the sofa.
- cushion — also, something that softens an impact, physical or financial: Their savings gave them a cushion in case either of them lost their job.
How to tell them apart
Location is the quickest test. A pillow lives on a bed and is shaped to support the head overnight. A cushion lives on chairs, sofas, and floors, and is there for general comfort while sitting or leaning, not specifically for the head. Both can be fluffed and both are soft fabric pads, which is where the confusion usually starts.
Cushion also does work pillow cannot: it can act as a verb, meaning to soften the effect of an impact, and it can describe anything that absorbs a shock, including a financial one, as in the extra padding cushioned her fall or the company's reserves cushioned it against the downturn.
