always used before a noun
: most important : chief principal
the main idea/point
the main goal/purpose
Speed is the main advantage of this approach.
The company's main office is located in New York.
the novel's main character
driving down the main road/highway
the main gate/entrance
This dish can be served as a main course or appetizer.
And now for the main event of the evening!
plural mains
1
: the largest pipe in a system of connected pipes
a gas main
a water main
2
British
a
: the system of pipes or wires for electricity, gas, or water
My radio runs either off batteries or off the mains.
—often used as mains before another nounWe haven't had any mains water/electricity since the storm.
b
: the place where electricity, gas, or water enters a building or room
Turn off the water at the mains.
Cite this Entry
“Main.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/main. Accessed 15 Apr. 2026.
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