By Mayo Clinic Staff. Erectile dysfunction â the inability to get and keep an erection firm enough for sex â is a common problem. You've likely seen advertisements for erectile dysfunction herbs or supplements to increase your sexual performance..
plate tectonics. In geology, a theory that the Earth's lithosphere (crust and upper mantle) is divided into a number of large, plate-like sections that move as distinct masses. See Notes at fault, Gondwanaland, See more at tectonic boundary.
In geologic terms, a plate is a large, rigid slab of solid rock. The word tectonics comes from the Greek root to build.. Putting these two words together, we get the term plate tectonics, which refers to how the Earth's surface is built of plates.