A Post-it Note (or sticky note) is a small piece of paper with a re-adherable strip of glue on its back, made for temporarily attaching notes to documents and other surfaces. A low-tack pressure-sensitive adhesive allows the notes to be easily attached, removed and even re-posted elsewhere without leaving residue. Originally small yellow squares, Post-it Notes and related products are available in various colors, shapes and sizes.
Although 3M's patent expired in 1997, "Post-it" and the original notes' distinctive yellow color remain registered company trademarks, with terms such as "repositionable notes" used for similar offerings manufactured by competitors. While use of the trademark 'Post-it' in a representative sense refers to any sticky note, no legal authority has ever held the trademark to be generic.
