What is required for an ocean trench to form

Trenches are formed by subduction, a geophysical process in which two or more of Earth's tectonic plates converge and the older, denser plate is pulled beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) the bend and form a steep, V - shaped depression.

Answer: Trenches are the V-shaped depression that are formed in the ocean when two distinct plates collides with one another, of which the denser plate (oceanic plate) gets subducted beneath the less denser plate (continental/oceanic plate), creating a subduction zone or the benioff zone.

Due to this subduction phenomenon, the V-shaped depression forms in the ocean which is known as the trench.