手早い答え
demais は1語の副詞・代名詞・形容詞、de mais は de が周囲の構文に属するとき2語です。
確実な見分け方は、英語から訳す前に、その単語の働きを見きわめることです。
それぞれの単語の働き
demais
too much, very, or the others
Use demais for excessive degree, strong intensity, or the remaining people and things.
de mais
more than expected or of more
Use de mais for a prepositional combination opposed to de menos or used after certain nouns and pronouns.
選び方
- demais: Choose demais if the sentence points to excessive degree, strong intensity, or the remaining people and things.
- de mais: Choose de mais if the sentence points to a prepositional combination opposed to de menos or used after certain nouns and pronouns.
例文
A palestra demorou demais.
The talk took too long.
Não vi nada de mais no relatório.
I saw nothing unusual in the report.
よくある落とし穴
The fixed phrase nada de mais is written separately. With the sense “excessively,” as in falou demais, use one word.
文脈の中で練習する
自分の実生活から文を一つ選び、二回書いてみましょう。一度はdemaisで、もう一度はde maisで。どちらも成り立ちそうなら、意味の違いを言葉にしてみましょう。