Sewage is the dirty mix that leaves our homes through pipes under the ground: waste from the human body, plus the used water from sinks, baths, and showers. It is the stuff itself, not the pipes. Cities hide it, but every town has to move it away and then clean it, or rivers and streets get sick. The word is ordinary and a little ugly; you hear it in news about leaks, smells, and water safety. Some people say “waste water” to sound milder. Though actually, not all used water is sewage — rain that runs off a road is a different stream, even if it may meet sewage later in the same pipes. Don’t use sewage for the network of pipes; that system is sewerage (or, in everyday talk, just “the sewers”).