Momme [mom-ee] is a Japanese word used as a unit of weight measurement for real silk. The higher the momme, the heavier and denser the weave will be.
During the process of silk production, the silk factory will adjust the density and yarn count of the silk thread to control the weight (or momme) of the fabric. With 22 momme charmeuse pillowcase, for example, the weft and warp of the silk fibers are woven closer together than they would be for a 19 momme charmeuse pillowcase.
Higher momme silk fabrics are also made with thicker yarn. In this way, momme is similar to thread count, which is commonly used to measure the weave of cotton sheets. 100% pure silk pillowcase or silk bed sheets with higher momme are likely to be of superior quality.