No. Silk is a fiber (the material). Satin is a weave (the way a fabric is woven) that creates a smooth, shiny face. So you can have satin made from silk (silk satin), but also from polyester, viscose, or cotton.

In stores, “satin” is often used to describe polyester satin. It can look shiny, but it usually feels different and performs differently than real silk. If you want the specific benefits of silk such as temperature regulation and a more luxurious feel, look for “100 percent silk” and a momme weight, especially when buying a silk pillowcase.

If you mainly want a smooth surface to reduce friction, cotton satin or viscose satin can also work, but it is not the same as silk.