- What's the difference between
- What rules should I follow to know which one to use?
- Could you provide examples showing their uses?
Más means 'more'
Mas means 'but', usually it can be replaced by 'pero'
They both have the same pronunciation(*) despite the accent, the accent is here to make clear what meaning is actually used. Note that 'mas' is uncommon in a casual conversation, it is mostly used in literature.
(*) That's only true if they are alone. In a complete sentence, the pronunciation may vary. Please, see Javi's comment for more details.
"Mas" is rather unfrequent - at least in every day speech, here in Argentina, but I suspect it's the same in many other places, based on movies, TV, books, etc. It even sounds a bit archaic.
You almost always will see and want to use "más", not "mas" (most of the times you read "mas", it's probably a "más" missing an accent).
How to tell them apart? A quick rule (that I'm making up right now so it's obviously not thorughly tested!) is remembering that "mas" means "but". So if you can replace it with "pero", it's "mas"; otherwise, it's "más".
A dumb example of both words in a sentence:
When you use "más" it means more.
When you use "mas" you are contrasting ideas, like "but".