The term 'WINDOW SILL' is composed of two words: 'WINDOW' and 'SILL'. The first word, 'WINDOW', refers to an opening in a wall or roof that allows light and air to enter a building. The second word, 'SILL', is defined as a LEDGE or strip of material that forms the bottom of a WINDOW frame. Together, the two words form the term 'WINDOW SILL', which is a flat surface that runs along the bottom of a WINDOW frame, providing support and protection from the elements.