A conduit is a structure or PASSAGE that allows the flow of liquids or gases. An AQUEDUCT is an artificial WATERCOURSE used to transport water from one place to another. A WATERCOURSE is a natural or artificial CHANNEL for water, such as a river, stream, or CANAL. A GUTTER is a shallow trough or CHANNEL along the edge of a roof that collects and carries away rainwater. A WATERWAY is a navigable body of water, such as a river, lake, or CANAL. An ARTERY is a blood vessel that carries oxygenated blood away from the heart to the body's tissues. A PIPELINE is a PIPE or system of pipes used to transport liquids or gases. A PASSAGE is a way through or around something, especially a route for travel or access. A SPOUT is a PIPE or hole through which liquid is poured or discharged. A DITCH is a long, narrow, open trench dug in the ground, typically to carry water away from a particular area. A CANAL is an artificial WATERWAY used for navigation, irrigation, or drainage. A MAIN is a large PIPE or DUCT that carries water, gas, or electricity to smaller pipes or ducts. A COURSE is a route or direction followed by a person or thing. A DRAIN is a PIPE or CHANNEL that carries off surplus liquid, especially rainwater or liquid waste. A TUBE is a long, hollow cylinder of metal, plastic, or other material used to convey liquids or gases. A SEWER is a PIPE or system of pipes used to carry away sewage or surface water. A DUCT is a TUBE or passageway in a building or machine for air, smoke, or liquid. A CHANNEL is a long, narrow part of a river, sea, or other area of water, typically connecting two larger areas of water. A PIPE is a TUBE or hollow cylinder used to convey water, gas, or other fluid substances.