A ditch with water can be used for drainage and irrigation.

With or without water it can be used as a barrier, as an alternative for a fence.

A trench is a long narrow ditch.

Types and applications include:

• Military - i.e. for trench warfare
• Geological - oceanic trench, eg Mariana Trench
• Gardening
• Archaeology - referring to an open excavation
• a temporary trench for burying a pipeline, cable, etc.