main (mains plural )
1 adj The main thing is the most important one of several similar things in a particular situation.
(=chief)
...one of the main tourist areas of Amsterdam...
2 If you say that something is true in the main, you mean that it is generally true, although there may be exceptions.
♦
in the main phrase
(=on the whole)
Tourists are, in the main, sympathetic people...
3 n-count The mains are the pipes which supply gas or water to buildings, or which take sewage away from them.
...the water supply from the mains...
4 n-plural The mains are the wires which supply electricity to buildings, or the place where the wires end inside the building.
(mainly BRIT)
...amplifiers which plug into the mains...