\▐rä-zәn, ▐ró-, dial▐ró-zәm\ n [ME, mod. of MF resine resin] (13c) An important “natural” resin, obtained from pine trees of several species by collection of exudates from cuts through the bark or by extraction from stumps, referred to as wood rosin (Merriam-Webster’s Collegiate Dictionary (2004), 11th edn. Merriam-Webster, Springfield, MA). Rosin is brittle and friable, and is used mostly for sizing paper. Modified rosins are used in printing inks, pressure-sensitive adhesives, and chewing gum. Two general kinds of rosin are commercially available: gum rosin obtained from living trees, and wood rosin obtained from dead wood, such as stumps and knots. Tall oil rosin, a by-product of the paper industry, is a chemically similar material, also known a colophonium and colophony (Flick EW (1991) Industrial synthetic resins handbook. Williams Andrew Publishing/Noyes, New York).