Gas line and Gas main

Gas line noun - A pipeline used to transport natural gas.

Gas main and gas line are semantically related in gas pipe topic. In some cases you can use "Gas main" instead a noun phrase "Gas line", when it comes to topics like gas pipeline, natural gas pipeline.

Gas main noun - A main that distributes gas.

Gas line and gas main are semantically related in gas pipe topic. You can use "Gas line" instead a noun phrase "Gas main", if it concerns topics such as gas pipeline, natural gas pipeline.