A trench is a long, narrow excavation in the ground, often deeper than it is wide. Trenches are commonly used in construction and engineering for various purposes, such as laying pipes, cables, or foundations. They can also be found in military contexts, where soldiers dig them for protection during combat. In geology, a trench refers to a deep, steep-sided depression in the ocean floor, often formed by tectonic plate movements. These underwater trenches, like the Mariana Trench, are some of the deepest parts of the Earth's oceans and are important for studying marine life and geological processes.