More jottings from Ciberdúvidas, this time about different ways of saying too many/much. There does seem to be an overlap between the uses, so I’ll just spread them out and see what’s what.
Demais
Can be:
- An adverb meaning “a heck of a lot”. Ele fuma demais seems to be “he’s a heavy smoker” and not “he smokes too much”
- An intensifier where it does the same job as the adverb but it underscores other adverbs or adjectives – A jarra é frágil demais; vai partir-se
- A kind of indefinite nouny-pronouny thing along the lines of “the surplus” or “the others”: Daquelas senhoras, uma comeu peixe, as demais comeram carne
- A way of saying “além disso”: Esse trabalho é muito difícil; demais, é mal pago [also spelled “ademais” in this case]
De Mais
Ciberdúvidas says it’s an adverb but it’s behaving like an adjective, expressing that the amount is excessive. It’s equivalent to “a mais”. It’s always referring to quantity, not degree. Comprei livros de mais
Demasiado
Can be
- An adjective and fulfills the same function as de mais. Note that, like other adjectives, the ending changes. It’s more commonly used in Portugal than in Brazil. Goes before the word it’s qualifying. Passam demasiados carros.
- An adverb, where it fulfills the same function as demais. Comi demasiado.
Luso 