Main means chief or most important, and also a large pipe for water or gas; mane is the long hair on the neck of a horse or lion. Remember: main has the same -ain ending as drain, which fits a water main.
The core difference
Main means most important, or a large supply pipe, whereas mane is the long hair on an animal's neck.
- main — most important, or a large pipe carrying water, gas or electricity: The main reason he quit was the long commute.
- mane — the long, thick hair on an animal's neck, or informally a person's thick hair: The lion shook its mane as it roared.
How to tell them apart
Main and mane are homophones, so the confusion only appears in writing. Main is the everyday word for something chief or primary: the main road, the main course, a burst water main. Mane belongs to lions, horses and, jokingly, people with impressive hair.
A quick trick is to link main to drain, since both end in -ain and a water main is a pipe. If you mean the hair on an animal's neck, it is mane. The common slip is writing "lion's main" or "the mane road" by ear.
