Whiten/ˈwaɪtn/ Definition 1 of 3Pro Tip 1/3Physical change Used when something's color actually becomes lighter, often through a chemical or physical process. Regular washing can help to whiten old linens. Pro Tip 2/3Gradual process The action of whitening something may be gradual and not immediate. Over time, the sun will whiten the colored fabric of the curtains. Pro Tip 3/3Natural whitening Refers to natural processes, like daylight causing colors to fade. The old paper will whiten further in the sunlight.