The word ‘sedimentary’ is derived from the Latin word sedimentum, which means settling.

• Rocks (igneous, sedimentary and metamorphic) of the earth’s surface are exposed to denudation agents, and are broken up into various sizes of fragments.
• Such fragments are transported by different exogenous agencies and deposited. These deposits through compaction turn into rocks. This process is called lithification.
• In many sedimentary rocks, the layers of deposits retain their characteristics even after lithification.
• Hence, we see a number of layers of varying thickness in sedimentary rocks like sandstone, shale etc.

Source: ForumIAS