A patch is a flat area of color change in the skin that is 1 cm or more wide.
Brownell I, Loomis CA, Koss T. Skin development and maintenance. In: Bolognia JL, Schaffer JV, Cerroni L, eds. Dermatology. 4th ed. Philadelphia, PA: Elsevier; 2018:chap 2.
Gawkrodger DJ, Ardern-Jones MR. Terminology of skin lesions. In: Gawkrodger DJ, Ardern-Jones MR, eds. Dermatology: An Illustrated Colour Text. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 7.